Fix Travis builds using appraisal gem

[md5]

This PR fixes the Travis builds by using different gemfiles for different versions of Ruby and some gem dependencies (notably rack 1.x and 2.x). These gemfiles are managed by the appraisal gem.

It also switches our build matrix from testing with jruby-head to testing with jruby-9.0.5.0, since jruby-head has some issues with bundler not being installed.

In addition to these changes, I have also enabled Travis's caching feature for Bundler. Hopefully this should speed up our test runs once the caches are primed. In my testing, it appears to have cut the aggregate build time by about a third.

[md5]

It's worth noting that Travis is now running tests for three Gemfiles for MRI version 2.2, 2.3, and head as well as JRuby 9.0.5.0. The three gemfiles test the default, latest dependencies as specified by the gemspec, rack 1.x with json 1.x, and rack 1.x with json 2.x.

If we decide to reduce the number of RVM/Gemfile combinations being tested, we can speed up the time needed for Travis to complete.

[coveralls]

Coverage decreased (-2.3%) to 94.505% when pulling def02d5 on appropriate:appraisal into 59eeeb1 on omniauth:master.

[coveralls]

Coverage decreased (-2.3%) to 94.505% when pulling def02d5 on appropriate:appraisal into 59eeeb1 on omniauth:master.

[md5]

Looking closer at the Gemfile.lock, it seems that json is only actually used as a dependency of coveralls, so I think we can safely minimize the combinations tested. I think we do need to test against rack 1.x and rack 2.x though.

[md5]

I've amended this branch to only have appraisal gemfiles for rack 1 and 2. I've locked the problematic coveralls dependencies (json and tins) in the base Gemfile. This should reduce the build matrix by a few builds and speed things up (although not on the first run since it will invalidate the caching due to new gemfile names).

[coveralls]

Coverage decreased (-2.3%) to 94.505% when pulling bbc29c0 on appropriate:appraisal into 59eeeb1 on omniauth:master.

[coveralls]

Coverage decreased (-88.8%) to 8.046% when pulling bbc29c0 on appropriate:appraisal into 59eeeb1 on omniauth:master.

[md5]

Travis! Y u NameError: uninitialized constant Hashie::Extensions::Array?

[md5]

Looks like this was broken because the build picked up a breaking change between hashie 3.4.4 and 3.4.5: hashie/hashie#367. The fix is here: hashie/hashie#368

I think I'll wait until the hashie release 3.4.6 is cut and retry this build.

[dblock]

I released hashie 3.4.6, please check it out.

[md5]

Thanks @dblock! I appreciate the proactive heads-up

[md5]

I think this is ready to merge. The Coveralls coverage reported here is not what it shows on the site, probably because I restarted the Travis build without pushing any new commits. I you look at the site, it shows a %2 drop to %94 and the differences look like differences between how coverage is reported across Ruby versions.

[suprnova32]

Thanks @md5!