`bundle install` doesn't always work -- sometimes it runs into errors
making HTTP requests, for whatever reason. This will cause Travis to
fail which is pretty annoying.
* Travis supplies an executable called `travis_retry` which will
automatically retry the command up to 3 times before really failing.
Tell Travis to use this when it runs `bundle install` before it
runs tests.
* In spec_helper, we create a Rails app and use this within the
test suite. This will also run `bundle install`. Unfortunately we
can't use `travis_retry` for this as it's a function and is not
available to us in Ruby-land, so use our own retry logic.
* Thanks to @sikachu!
Travis will now runs `bundle install --deployment` if it detects that
the project has `Gemfile.lock`. However, there's a problem in Bundler
deployment install that cause it not installing `bundler` gem into
`vendor/bundle` directory, which causes `require 'bundler'` to fail.
* Add Ruby 2.0 support to the Appraisals
* Update travis to test 2.0.0 with the 3.2 gemfile. Clean up the travis
matrix to favor the include syntax over exclude.
* Edit gemfile.locks to point to relative paths.
