Update INSTALL.md - fixes #152

[absorber]

Added documentation about perl dependencies to reflect this issue - #152

[ncanceill]

Excellent, now I can send a PR to your own branch with my own small changes to what you changed.

[ncanceill]

Oh, one last thing, when I asked you to add "fixes" to the PR description, I was not talking about the PR title, but the description text (your first comment).

[RichiH]

Can you rewrite this to state that you only need ronn in master, not release?

#167 should also make prove opportunistic.

I can easily rewrite it myself, but I guess you want the honour of the patch :)

[alerque]

@RichiH This was another of the automatic GitHub closures, it looks like the same reason applies (upstream fork removed). I would re-submit it, but I think this one is obsolete. The things it adds are no longer required for install, only for test, and that is properly document later in the file.