SPARK-1650: Correctly identify maven project version

Better account for various side-effect outputs while executing
"mvn help:evaluate -Dexpression=project.version"

Author: Rahul Singhal <rahul.singhal@guavus.com>

Closes #572 from rahulsinghaliitd/SPARK-1650 and squashes the following commits:

fd6a611 [Rahul Singhal] SPARK-1650: Correctly identify maven project version
(cherry picked from commit 7b2527d74deac9512f8ee9ad6d4b060f05e1ab26)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>