improve FollowRedirects middleware + support for 307
refactor redirect middleware implementation & tests

In tests, avoid using `send` to work with dynamic HTTP methods. Instead
use `new_stub` and `run_request` methods that accept HTTP method as
argument.
ensure redirect doesn't forward body for requests transformed to GET
redirect middleware: clear response values in env hash between requests
Add a standards_compliant option to properly handle HTTP 302
Merge pull request #25 from nbibler/standards_compliant_302

Add a standards_compliant option to properly handle HTTP 302
have OAuth correctly handle non-urlencoded request bodies
make OAuth middleware compatible again with Faraday 0.7
fix redirects spec for Faraday 0.8
redirects: improve docs for `:standards_compliant`
force code style checks with cane

Fix too long line lenghts, add missing docs for classes.
only run coverage + cane on MRI 1.9.3
v0.8.5
don't bother generating coverage HTML report on CI
Explicitly specify language
Test in both 1.8 and 1.9 mode on JRuby and Rubinius
fix RackCompatible to not lose request env values

Fixes #27
v0.8.6
make Rack::Cache test more strict by not tolerating logged exceptions

Because of the missing `Rack::Cache::Storage.instance.clear` line in
test setup, some operations in the test were actually silently failing
due to uninitialized cache dirs. This ensures future exceptions in
Rack::Cache don't go unnoticed.

Closes #28
Allow custom mash classes at the instance level.