CDAP-527: update SparkPageRank program to read directly from stream

Conflicts:
	pom.xml
	src/main/java/co/cask/cdap/guides/BackLinksHandler.java
CDAP-527: added scope to hadoop dependency
CDAP-527: changes in docs
Added unit test
move the test to right place
Merge pull request #20 from cdap-guides/release/2.6.0

Release/2.6.0