Big ol' refactor

Directive now takes expressions for attrs and is much more responsive
to changes—it will reparse or reformat the input value if
min/max/format/modelFormat/viewFormat are modified.
gitignore node_modules/
Dollar prefix moment service props/methods

Check if moment has already been extended
gitignore test coverages
Begin adding tests

Only the service at this point
Begin work on directive tests

Rename provider.spec.js to service.spec.js
More tests!
Test min/max
Fix bug with undefined min/max at time of init
Remove duplicate expect statement
Test arrays for min/max
View-side testing of min/max attrs
Add test for changing min/max attrs
Rename vars to be a little more descriptive
Fix test
Test view- and model-format attrs
Fix bug where changing model formats with empty view would set model to undefined
On invalid min/max, set related moments to null
Use karma.conf instead of test.conf
Add an indexOf func from Angular src