More ESM

[TehShrike]

These changes do a few things, most importantly:

• the operations entry point now exports each function individually as a named export, allowing tree-shaking
• the tests now run off of the current live code, instead of the compiled UMD build
• the default entry point for ES modules is the live code, instead of a build, which allows tree-shaking
• there is no more ES build, but there is a CJS build, allowing browserify to bundle chromatism without pulling in the unnecessary UMD wrapper
• getting the tests working off the live code again exposed a bug in the convert operation, where color objects that held arrays weren't being handled at all

I also tossed a .travis.yml file into the project so that @toish can go to https://travis-ci.org/toish/chromatism and flip the switch, giving us automated tests.

[graypegg]

Not at home at the moment, but I turned on travis CI! Colour objects held in arrays were being processed in the old api as a list of colours which could be multi-dimensional, so that functionality may need to be moved into convert.js!

[TehShrike]

The tests are passing now as of this PR, but after this is merged you may want to add some more tests to assert that the old conversion functionality is still retained by the current convert operation.