added RBENV instructions, removed RVM, added sqlite3 installation instructions.
added RBENV instructions, removed RVM, added sqlite3 installation instructions.

spookysalsa/medermade.github.io,spookysalsa/medermade.github.io,bounceflick/bounceflick.github.io,davidckim/davidckim.github.io,davidckim/davidckim.github.io