Add FreeBSD installation instructions

Make man pages parseable with `whatis`

Outputs the "NAME" section in roff format to fix the following:

    mandb: warning: ... whatis parse for hub-alias(1) failed

Fixes https://github.com/github/hub/issues/2025

Fixes https://github.com/github/hub/issues/2036

Assume that 4xx responses will be the same given the same request, so
these responses should be subject to caching too.

Avoids caching 403 because that is the status returned when GitHub API
limit is hit.

Continue not caching 5xx responses because they indicate server errors,
so it's possible that a 2nd request of identical parameters succeeds.

Allow raw request body via `hub api --input <FILE>`

Fixes #2022

Consistent ordering and `--format` support for `ci-status`

Statuses are now sorted the same as in the GitHub web interface:

- failing first;
- then pending;
- then success/neutral;
- everything in-between is sorted alphabetically.

Fixes #2021

Add HTTP request/response headers functionality to `hub api`

Fix subcommand execution under WSL

Makefile: fix arguments to go, not matching what go expects

- HTTP response is now printed on stdout regardless of HTTP status
- No longer print an extra newline after HTTP response body
- No more `Error: HTTP {STATUS}` message on stderr
- hub exits with status 22 instead of 1

This caused gcc to receive the actual argument "''" or for example
"'-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'" and then error
with
gcc: error: '-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now': No such file or directory

Furthermore, the trimpath arguments tried to trim an actual path
resembling "'$PWD'", which did nothing as the literal single quotes were
not valid in this context.

Both issues can be fixed by assigning arguments to the go compiler using
the argv notation { "-flag", "argument" } rather than { "-flag=argument" }.

[ci skip]

[ci skip]

Allows sending `api.github.com` OAuth token to all `*.github.com`
subdomains. In case `git.my.org` is an Enterprise instance, this allows
sending the token to `git.my.org` and all of `*.git.my.org`.

https://travis-ci.org/github/hub/jobs/484769927

[ci skip]