ruby-local-exec was ruby specific.

Does no apply for php and is being deprecated in any case, https://github.com/sstephenson/rbenv/wiki/ruby-local-exec , lets drop it now
Updated with changes from latest (0.4.0) rbenv.
Removed unuseful things
We've got all this help so display it then
consistency: phpenv help add summary
Also show help with --help
Don't show version on --version again
Add global --unset to docs
phpenv install to use same help system