Made spark_ec2.py PEP8 compliant.

The change set is actually pretty small -- mostly whitespace changes. Admittedly this is a scary change due to the lack of tests to cover the ec2 scripts, and also because indentation actually impacts control flow in Python ...

Look at changes without whitespace diff here: https://github.com/apache/spark/pull/891/files?w=1

Author: Reynold Xin <rxin@apache.org>

Closes #891 from rxin/spark-ec2-pep8 and squashes the following commits:

ac1bf11 [Reynold Xin] Made spark_ec2.py PEP8 compliant.
Add Shortest-path computations to graphx.lib with unit tests.

Adds a landmark-based shortest-path computation to org.apache.spark.graphx.lib.

Author: Andres Perez <andres@tresata.com>
Author: Koert Kuipers <koert@tresata.com>

Closes #10 from apache/spark and squashes the following commits:

88d80da [] Merge from master.
c9d1ee8 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
47e22db [Andres Perez] Remove algebird dependency from ShortestPaths.
44d19e5 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
4986f80 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
25fbe10 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
9ee0d89 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
745a7a1 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
9319fac [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
d47865f [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
ba6e530 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
5c5b197 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
ee9d90b [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
2d5e788 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
6cd90a5 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
2cbfe45 [Koert Kuipers] Merge branch 'master' of https://github.com/apache/spark
a3bdb0e [Koert Kuipers] Merge branch 'master' of https://github.com/apache/incubator-spark
f8f6d91 [Andres Perez] Revert "Add Shortest-path computations to graphx.lib with unit tests."
7496d6b [Andres Perez] Add Shortest-path computations to graphx.lib with unit tests.
Fix style errors
Remove unnecessary VD type param, and pass through ED
Improve ShortestPaths documentation