Add support for gems.rb and gems.locked, closes #524.

[remomueller]

This pull request merges together @mizalewski's and @JuPlutonic's changes on #538 to support gems.rb and gems.locked files in spring. I've also wrapped the tests to only run on Ruby 2.0.0 or higher. Let me know if anything else is needed, thanks!

[JuPlutonic]

@remomueller would you like to add gem install sqlite at the end of the Ubuntu requirements. Now all Travis integration tests that depends on sqlite is failing.

[remomueller]

Sure, what file should I add that too? Should I do it similar to your latest pull request?

[JuPlutonic]

Yes, I'm tossing gems sqlite3 ana nokogiri and their versions to get the greens in Travis

[remomueller]

I see the changes in .travis.yml, but it doesn't appear that it makes all the Travis tests pass? I can always rebase this pull request after the master branch has tests passing again as well, instead of adding those fixes into this pull request.

[JuPlutonic]

Hmm, Ok let me summarize bellow what I'm getting:

TRAVIS CI acceptance tests:

1. nokogiri 1.6.8 for ruby 19.1, 2.0.0, 2.1.10, 2.2.10

2. i18n 1.5.1 for ruby 2.1.10, 2.2.10

3. sqlite3 1.6.0 preinstalled before rails if rails 4.2.0, 5.0.0

Mical' Zaleski's PR in his branch* what I used to test gems.rb realization also accidentally pushed to master

1. Is this *branch's Patch-1 needed? It got last changes from community (Spring binstub fails when BUNDLE_APP_CONFIG is set #545 rails console will not suspend #361)
   bc40139

[JuPlutonic]

sqlite3 also suggested in #586, but I think that gemspec's add_development_dependency is a better place.
@travis-ci please re-run tests👏

[rafaelfranca]

Can you rebase this PR?

[remomueller]

Hi @rafaelfranca, I rebased the PR back onto master, let me know if any other changes are needed, thanks!

[n-rodriguez]

Hi there! Any news?