Cut version 0.17.0

Some people refer to releasing a new version of a gem as "cutting"
a new version. This commit marks the release of overcommit 0.17.0,
and follows the pattern of commits from previous releases.

Change-Id: I9557ea85f409169d79c6e617cbf016b1ecb95a23
Reviewed-on: http://gerrit.causes.com/42091
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@brigade.com>

Author: lencioni

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Overcommit Changelog
 
-## master (unreleased)
+## 0.17.0
 
 * Change commit hook header text to bold instead of bold white so that it
   displays on terminals with a white background

lib/overcommit/version.rb

@@ -1,4 +1,4 @@
 # Defines the gem version.
 module Overcommit
-  VERSION = '0.16.0'
+  VERSION = '0.17.0'
 end