Removes the X-Runtime header from ActionController::Benchmarking

The `Rack::Runtime` middleware now provides this header

Backport Rack session skip

Builder 3.2.2

i18n 0.4.1

Don't run tests on 1.9.3

Disable auto-generated form field IDs by passing nil for "id" attribute

Previously it was not possible to opt out of auto-generated ID values
for various form fields.

Freeze ERB string literals

Fix fragment caching in mixed encoding scenario

Ruby 2.1

To reduce ambiguity between char- and byte-based operations, explicitly
do byte operations when extracting the fragment that needs to be cached.

Remove CGI support