simplify null guard
Merge pull request #19 from davidchambers/guard

simplify null guard
Add trivial IsForeign Foreign instance
Merge pull request #21 from MichaelXavier/isforeign-foreign

Add trivial IsForeign Foreign instance
Add Eq instance for ForeignError

The use case is uncommon here, but this comes up a lot in testing. If
you're testing an IsForeign instance, you'd want to assert equality on F
which is Either ForeignError a.
Merge pull request #22 from MichaelXavier/eq-foreignerror

Add Eq instance for ForeignError
Update generated docs and grunt task for pscDocs
Update travis build to always use latest release
add ES3 fallbacks for Array.isArray and Object.keys