Merge pull request #498 from ScrapCodes/python-api. Closes #498.

Python api additions

Author: Prashant Sharma <prashant.s@imaginea.com>

== Merge branch commits ==

commit 8b51591f1a7a79a62c13ee66ff8d83040f7eccd8
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Fri Jan 24 11:50:29 2014 +0530

    Josh's and Patricks review comments.

commit d37f9677838e43bef6c18ef61fbf08055ba6d1ca
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Thu Jan 23 17:27:17 2014 +0530

    fixed doc tests

commit 27cb54bf5c99b1ea38a73858c291d0a1c43d8b7c
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Thu Jan 23 16:48:43 2014 +0530

    Added keys and values methods for PairFunctions in python

commit 4ce76b396fbaefef2386d7a36d611572bdef9b5d
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Thu Jan 23 13:51:26 2014 +0530

    Added foreachPartition

commit 05f05341a187cba829ac0e6c2bdf30be49948c89
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Thu Jan 23 13:02:59 2014 +0530

    Added coalesce fucntion to python API

commit 6568d2c2fa14845dc56322c0f39ba2e13b3b26dd
Author: Prashant Sharma <prashant.s@imaginea.com>
Date:   Thu Jan 23 12:52:44 2014 +0530

    added repartition function to python API.