Add specs for Yaks::Sinatra, classic and modular

[fidothe]

These are simple specs: they verify that for a given Accept header, a trivial Sinatra app with a trivial set of Yaks mappers will return a viable response with the correct mime type and explicit charset. Both a modular and a 'classic' Sinatra app are tested.

The MediaType class in spec/integration_helper.rb uses the HTTP spec's definition of the Content-Type header (and other media type headers) to parse a media type string and extract type and parameter parts. It's not ludicrous-real-world-example proof, but it should be more than enough for good-faith attempts at spec adherence of the kind expected from Sinatra and from Yaks.

This commit also remodels the Yaks::Sinatra namespace so that it's Yaks::Sinatra and not Sinatra::Yaks. Auto-registration for classic apps is verified, as is explicit registration for modular apps.

Notes are added to the README regarding correct usage in both classic and modular modes.

Files are Rubocop checked.

[plexus]

:heart_eyes:

Getting some timeouts on Travis installing gems. I restarted the build.

[janko]

Apparently the latest version of Mutant (0.8.0) requires Ruby >= 2.1.

[plexus]

And rspec 3.3. I'm fine with pinning mutant to ~> 0.7.0 for the time being until we get a chance to upgrade. Ruby 2.1 shouldn't be a big issue as it's enough to run mutant against the latest stable MRI, but I haven't looked yet at how involved upgrading RSpec would be.

[fidothe]

What's the issue with RSpec? I just got whatever came down when I bundle installed (all the tests pass locally on 2.2)

[plexus]

Never mind. There doesn't seem to be a real issue. Latest mutant relies on RSpec 3.3, and I wasn't sure if we were already 3.3-compatible. It seems things run fine though, just a few new warnings.

@janko-m is right though, the issue with the failing tests is that all builds in the matrix try to install mutant, but on Ruby < 2.1 that fails.

I just pushed an update to master, could you try rebasing?

[fidothe]

ha, i just committed essentially the same changes, except that I also stopped generating the mutant rake task on Ruby < 2.2. will pull your changes and revise my version number down in the rakelib file

[fidothe]

Rebased and passing the tests :-)

[plexus]

Ugh now I need to find an original gif :P

[plexus]