Experiment with relaxed test dependencies

[jch]

This PR always chooses the latest gem for a given ruby version for testing.

[jch]

Hmmm not fantastic. It might be better to experiment with different gemfiles within travis.

[simeonwillbanks]

Relaxing the dependencies is a win for users, so their applications have more freedom. However, all the gems require a specific configuration for the tests to pass.

👍 multiple gemfiles for two reasons:

1. Passing build
2. Documentation around known working dependencies

[jch]

Quick update, it looks like we get some failures with the latest gemoji (2.1.0)

  1) Failure:
HTML::Pipeline::EmojiFilterTest#test_uri_encoding [/Users/jch/projects/html-pipeline/test/html/pipeline/emoji_filter_test.rb:21]:
Expected /https:\/\/foo\.com\/emoji\/%2B1\.png/ to match "https://foo.com/emoji/unicode/1f44d.png".


  2) Failure:
HTML::Pipeline::EmojiFilterTest#test_custom_asset_path [/Users/jch/projects/html-pipeline/test/html/pipeline/emoji_filter_test.rb:34]:
Expected /https:\/\/foo\.com\/%2B1\.png/ to match "https://foo.com/unicode/1f44d.png".

[jch]

#129 may have some hints.

[jch]

#159 fixes gemoji related CI failures.

[jch]

Closing this because it doesn't feel right to try to couple our tests to external dependencies. A better approach would be to extract out filters that depend on external dependencies to their own gems.

[simeonwillbanks]

👍 own gems. Maybe we open a new issue to discuss?