Bump develop to cdap 2.7 snapshot dependency
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
Fix version for 2.6.0 compatible branch