Merge pull request #1 from almende/develop

Sync with upstream
Merge pull request #2 from almende/develop

Merge in upstream changes
Merge pull request #3 from almende/develop

Pull in upstream
Merge branch 'develop' of github.com:Gillingham/vis into develop
Correct type for stack option, docs and code use stack, but Timeline.js
used stacking for the default, making it not stack by default.
Merge pull request #106 from Gillingham/develop

Fix typo in Timeline.js for stack option