chore: cleanup stale branches

[DanielRuf]

Currently we have many stale branches. I'm not sure if we still need some of them but I would suggest that we delete all obsolete branches.

Let's define which can be safely deleted.

https://github.com/materializecss/materialize/branches/stale

@materializecss/members

[warrenrodrigues]

I'm all for deleting obsolete branches. And something needs to be done about master branch as well.
The contributing document refers to 'master', which can cause confusion, because the primary branch is v1-dev. Perhaps we can update the contributing document to reflect this (at least in an example below.)

[roiLeo]

Most of these branch have more than 600 commit behind, i think we can simply delete them.

[ChildishGiant]

Yea, I really think that calling master "v1-dev" is not good and should be tackled. Ideally master is stable and each version will get it's own branch that is then merged when stable.

[DanielRuf]

I have gone ahead and deleted all stale branches with no new commits and which are many commits behind.

These stale branches are left:

[ChildishGiant]

From a glance, the rollup branch has some changes that would fix #44 but obviously it was made by someone who's not on our project and with an end goal that's not entirely clear. I think unless we are actively aiming to introduce similar features or have the person on board we can probably nix them all.

[ChildishGiant]

Would love people to have a look at #186

[ChildishGiant]

All done!