git hooks for IPython
add these to your .git/hooks
For now, we just have post-checkout and post-merge,
both of which update submodules and attempt to rebuild css sourcemaps,
so make sure that you have a fully synced repo whenever you checkout or pull.
To use these hooks, run ./install-hooks.sh.
If you havn't initialised and updated the submodules manually, you will then need to run git checkout master to activate the hooks (even if you already have master checked out).