Update README.md

incorrect capitalization in ARApp.jar for the sample app. It was ARapp.jar, should be ARApp.jar
Merge pull request #62 from jeffastorey/patch-1

Update README.md.  Thank you, Jeff!
Mostly fixing typos...
Fixed extension building to build app first.  Closes #63
Updated spark for newer interfaces (builds)
Attempt at ivy resolution of Spark dependencies.
Improved paramter message.
Modified default arguments.
Updated serialization for int aggregates.
Merge branch 'master' into spark
Spark assembly on classpath.
Spark dependency fetching in ant, some other restructuring.
Ignoring eclipse classpath changes...
Documentation changes.  Argument simplification
 Notes on implementing ar.Renderer
Removed unused annotation.
Merge branch 'master' into spark
RDDRenderer is now an ar.Renderer implementation
Next-step note.
DRAFT mapPartitions (does not work...)