* Added a helm interface to all the things return by xref-index

[antoineB]

This a proof of concept to use the helm interface to browse the xref entries.

There is also a fix to load-collections-xref for my configuration, don't know what is wrong.

[greghendershott]

Thank you very much for the pull request.

1. I think the Travis CI build is failing because helm isn't installed by default. Which is a good point -- it won't be installed for all users. Can you change this to check at runtime in the usual way, using fboundp?
2. Namespacing function names prefixes: I think the functions named helm-racket-* should instead be either
   • racket-helm-* if they're "public" (such as a user command)
   • racket-helm--* (note the extra -) otherwise
3. That's interesting you're seeing a problem with load-collections-xref. Can you say more about that? It seems like part of this PR is a bug fix, i.e. the problem you're experiencing would affect the scribble-doc/html function, too, as used by racket-describe. Was racket-describe not working for you (prior to the change you made here)?

[antoineB]

I will change according to point 1 and 2.

For the point 3, yes racket-describe wasn't working before the fix, i use racket minimal release 6.1.