Update README.md
Bumping Rails version (4.1.2 -> 4.1.4)
Merge pull request #1 from feigner/master

Bumping Rails version (4.1.2 -> 4.1.4)
Upped the Ruby version from 2.1.0 to 2.1.2. Upped the Rails version from 4.1.4 to 4.1.6. Changed the box image to the next Ubuntu version (14.04). Added build-essential libraries so that Ruby installs properly.