Allow use of core.commentchar when creating git commit message

Fixes #81
Adding use of commentchar config and edit changelog
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch jwhitcraft-master
# Changes to be committed:
# 	modified:   Changelog.md
# 	modified:   lib/models/git-commit.coffee
Prepare 3.6.1 release