fix(package.json): move q to dependancies since it is required to run

While trying to run git_changelog after a `npm install git-changelog --save-dev`, I
found I was missing q, which is not installed when added to a project
this way.
fix(git_changelog_generate): pass tag if it exists to gitReadLog

Previously if a tag was found the script would try to find commits
between undefined..HEAD. By passing the tag, it now finds tags between
tag..HEAD.

Closes #5.
Merge branch 'fix-tags'