Revert "SPARK-1433: Upgrade Mesos dependency to 0.17.0"

This reverts commit 12c077d5aa0b76a808a55db625c9677a52bd43f9.
Update tuning.md

http://stackoverflow.com/questions/9699071/what-is-the-javas-internal-represention-for-string-modified-utf-8-utf-16

Author: Andrew Ash <andrew@andrewash.com>

Closes #384 from ash211/patch-2 and squashes the following commits:

da1b0be [Andrew Ash] Update tuning.md
Remove Unnecessary Whitespace's

stack these together in a commit else they show up chunk by chunk in different commits.

Author: Sandeep <sandeep@techaddict.me>

Closes #380 from techaddict/white_space and squashes the following commits:

b58f294 [Sandeep] Remove Unnecessary Whitespace's