Deprecate gist5210270 package.

Move unofficial tests of gist4727543 package into a real example test.
Use build.ImportComment.
Update Travis to use Go 1.4.
Travis: Update import path for cmd/vet.
Add support for fetching RepoRoot in VcsState.

Fetch it as part of UpdateVcsFields.
Use build.ImportComment only in Go 1.4.

Add support for Go 1.3 for a while longer.
Fixes #13.
Switch to fork of gopherjslib since upstream is broken.

See issue go-on/gopherjslib#4.