Add an option to ignore pull-request templates.

[tomprince]

#22 added support for using the github pull request template to populate the pull request body.

However, when using git-pull-request in automation, this has a couple of issues:

• it always opens the editor on the message, even if it is isn't going to be used (this can be worked around by setting EDITOR=true)
• the issue template isn't necessarily appropriate for PRs generated by automation.

i t would be nice if there was a setting that could be added to the git config to disable looking for the PR template.