Add Code Style and some dev docs (#286)

CODE_STYLE.md

+# Code Style
+
+We follow the standard Go style using gofmt, but with a few extra
+considerations.
+
+## Linters
+
+We use `gometalinter` to run a number of linters, the exact list can be found
+in [linter.json](linter.json). Some of these are slow and expensive to run, but
+a subset can be found in [linter-fast.json](linter-fast.json) that run quickly
+enough to be run as part of an IDE.
+
+For rare cases where a linter is giving a spurious warning, it can be disabled
+for that line or statement using a [comment directive](https://github.com/alecthomas/gometalinter#comment-directives), e.g.
+`// nolint: gocyclo`. This should be used sparingly and only when its clear
+that the lint warning is spurious.
+
+
+## HTTP Error Handling
+
+Unfortunately, converting errors into HTTP responses with the correct status
+code and message can be done in a number of ways in golang:
+
+1. Having functions return `JSONResponse` directly, which can then either set
+   it to an error response or a `200 OK`.
+2. Have the HTTP handler try and cast error values to types that are handled
+   differently.
+3. Have the HTTP handler call functions whose errors can only be interpreted
+   one way, for example if a `validate(...)` call returns an error then handler
+   knows to respond with a `400 Bad Request`.
+
+We attempt to always use option #3, as it more naturally fits with the way that
+golang generally does error handling. In particular, option #1 effectively
+requires reinventing a new error handling scheme just for HTTP handlers.
+
+
+## Line length
+
+We strive for a line length of roughly 80 characters, though less than 100 is
+acceptable if necessary. Longer lines are fine if there is nothing of interest
+after the first 80-100 characters (e.g. long string literals).
+
+
+## TODOs and FIXMEs
+
+The majority of TODOs and FIXMEs should have an associated tracking issue on
+github. These can be added just before merging of the PR to master, and the
+issue number should be added to the comment, e.g. `// TODO(#324): ...`
+
+
+## Visual Studio Code
+
+If you use VSCode then the following is an example of a workspace setting that
+sets up linting correctly:
+
+```json
+{
+    "go.gopath": "${workspaceRoot}:${workspaceRoot}/vendor",
+    "go.lintOnSave": "workspace",
+    "go.lintTool": "gometalinter",
+    "go.lintFlags": ["--config=linter-fast.json", "--concurrency=5"]
+}
+```

CONTRIBUTING.md

@@ -3,6 +3,19 @@
 Everyone is welcome to contribute to Dendrite! We aim to make it as easy as
 possible to get started.
 
+Please ensure that you sign off your contributions! See [Sign Off](#sign-off)
+section below.
+
+## Getting up and running
+
+See [INSTALL.md](INSTALL.md) for instructions on setting up a running dev
+instance of dendrite, and [CODE_STYLE.md](CODE_STYLE.md) for the code style
+guide.
+
+We use `gb` for managing our dependencies, so `gb build` and `gb test` is how
+to build dendrite and run the unit tests respectively.
+
+
 ## Picking Things To Do
 
 If you're new then feel free to pick up an issue labelled [easy](https://github.com/matrix-org/dendrite/labels/easy).

INSTALL.md

@@ -5,7 +5,7 @@ Dendrite can be run in one of two configurations:
  * A cluster of individual components, dealing with different aspects of the
    Matrix protocol (see [WIRING.md](./WIRING.md)). Components communicate with
    one another via [Apache Kafka](https://kafka.apache.org).
- 
+
  * A monolith server, in which all components run in the same process. In this
    configuration, Kafka can be replaced with an in-process implementation
    called [naffka](https://github.com/matrix-org/naffka).
@@ -17,7 +17,7 @@ Dendrite can be run in one of two configurations:
  - For Kafka (optional if using the monolith server):
    - Unix-based system (https://kafka.apache.org/documentation/#os)
    - JDK 1.8+ / OpenJDK 1.8+
-   - Apache Kafka 0.10.2+ (see https://github.com/matrix-org/dendrite/blob/master/travis-install-kafka.sh for up-to-date version numbers)
+   - Apache Kafka 0.10.2+ (see [travis-install-kafka.sh](travis-install-kafka.sh) for up-to-date version numbers)
 
 
 ## Setting up a development environment
@@ -34,7 +34,7 @@ go get github.com/constabulary/gb/...
 gb build
 ```
 
-If using Kafka, install and start it:
+If using Kafka, install and start it (c.f. [travis-install-kafka.sh](travis-install-kafka.sh)):
 ```bash
 MIRROR=http://apache.mirror.anlx.net/kafka/0.10.2.0/kafka_2.11-0.10.2.0.tgz
 
@@ -108,7 +108,7 @@ The following contains scripts which will run all the required processes in orde
 
 ```
 
-                                         /media   +---------------------------+ 
+                                         /media   +---------------------------+
                       +----------->+------------->| dendrite-media-api-server |
                       ^            ^              +---------------------------+
                       |            |            :7774