Some clean up in build/docs

(a) Deleted an outdated line from the docs
(b) Removed a work around that is no longer necessary given the mesos version bump.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #382 from pwendell/maven-clean and squashes the following commits:

f0447fa [Patrick Wendell] Minor doc clean-up

docs/index.md

@@ -67,8 +67,6 @@ In addition, if you wish to run Spark on [YARN](running-on-yarn.html), set
 
 Note that on Windows, you need to set the environment variables on separate lines, e.g., `set SPARK_HADOOP_VERSION=1.2.1`.
 
-For this version of Spark (0.8.1) Hadoop 2.2.x (or newer) users will have to build Spark and publish it locally. See [Launching Spark on YARN](running-on-yarn.html). This is needed because Hadoop 2.2 has non backwards compatible API changes.
-
 # Where to Go from Here
 
 **Programming guides:**