Added TwitterInputDStream from example to StreamingContext. Renamed example TwitterBasic to TwitterPopularTags.

As part of this, changed our Scala 2.9.2 Kafka library to be available
as a local Maven repository, following the example in
(http://blog.dub.podval.org/2010/01/maven-in-project-repository.html)

Added the io.spray JSON library

fix SequenceFileRDDFunctions to pick the right type conversion across Hadoop
versions