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>
default tags to empty set on export Pull Request #137
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
readme for Pull Request #137
Fix a typo in the name of the level
Merge pull request #142 from rogererens/patch-1

Fix a typo in the name of the level
beginning of graph file
treeCompare mod
WIP for moving
readme for Pull #142
code move
tag loading from trees now works
switch specs
write correct one
added test but not passing for weird reason
Update manyRebases.js

I found a solution which only takes 4 commands.