removed an extra reference to rails 3

added section on postgres, removed references to mysql

removed references to ruby 1.9, updated latest recommended ruby

removed references to rails 3, we're only using rails 4 now

Merge pull request #1 from allaboutdrama/patch-1

Update README.md

updated link to homebrew install

fixed up a typo re running rbenv init

removed extra notes at the end.

added TBD section

added section on installing rails

added mysql section

added installing ruby section

added rbenv and ruby-build sections

General cleanup and added Git and subl sections.