removing sqlite requirement as sqlite3 is included in all versions of Mac OS X

Homebrew warns when trying to install sqlite on Mac OS X that: "Mac OS X already provides this software and installing another version in parallel can cause all kinds of trouble."
Merge pull request #1889 from demetrios/patch-1

removing sqlite requirement for OS X (homebrew)
extra check and info for packages_custom, fix #1888
Merge branch 'master' of github.com:wayneeseguin/rvm