merge-target-branch failing on git config with too many arguments

[initvector]

The portion of merge-target-branch.sh responsible for configuring the GitHub user does not quote its values. This means the values can be treated as multiple arguments. For example:

1. git log --format='%an' $CIRCLE_SHA1^! could return "John Q Doe".
2. The outer command then becomes git config --global user.name John Q Doe.
3. Git rejects the command and the overall script fails, because there are too many arguments. "John Q" would technically complete successfully, although the global value of user.name would actually be "John".

ci-scripts/merge-target-branch.sh

Lines 34 to 36 in 3c014de

	# setup the github user
	git config --global user.email $( git log --format='%ae' $CIRCLE_SHA1^! )
	git config --global user.name $( git log --format='%an' $CIRCLE_SHA1^! )