Fix fast-forward for horizontal graphs

v1.6.1

Merge develop into master

Add fast-forward option for merges

Now you can do feature.merge(develop, { fastForward: true }); to perform a fast-forward merge if possible.

If fast-forward is not possible, it will fallback to regular merge.

Enhance emitted events

• Canvas event handlers can be disposed from the consumer end with gitgraph.dispose() - #128
• Click handlers receive the original event objects so you can identify the click type, for instance - #129

Add tooltipDisplay to commit options

See #119.

Fix offsetX and offsetY for older FF

See #116

Add the possibility to display tag without box

See #113.

Add the possibility to change the initial CommitOffsetX and CommitOffsetY

See #109.

Fix branches from previous commit + events support for FF < 39

See #86 & #107.

Restore line dash after applying it to branch

See #106

Fix tag alignment

See #103