Updated README to give more information about libraryDependencies

I had trouble getting set up because I am using Scala 2.11.1 for which a
blueprints-scala version could not be found.  It was necessary to explicitly
set the dependancy to 2.9.2
Fixed some of my grammar
Missed a word from my last update

Just needed to add 'error' as pointed out by anvie
Merge pull request #22 from aembleton/master

 Updated README to give more information about libraryDependencies