Git Tag: Initial support for tagging

Branching in git even more useful if using tags. Simulate relase branches,
maintenance branches and so on is therefore really useful in this tool.

Now, rudimentary tagging is implemented, where tags can be attached to the
commits, and referenced by for exmapmle git checkout

Signed-off-by: Max Sikström <msikstrom@op5.com>
Cleanup + fixed a typo

A typo (TagsCollection vs. TagCollection) made levels crash when loading.

There where still lot of stuff left for handling master branch in the visTag
code, because visTag is a modified version of the visBranch-object. Therefore,
clean up asome unused code

Signed-off-by: Max Sikström <msikstrom@op5.com>
Revert index.html and bundle to keep pull request small

Signed-off-by: Max Sikström <msikstrom@op5.com>
Add a string for bad-tag-name

Signed-off-by: Max Sikström <msikstrom@op5.com>
Merge branch 'tagSupport' Pull Request #137 Issue #134

Conflicts:
	src/js/git/index.js
change to headless to support tags and dont break all tests Pull Request #137 Issue #134