Add text to timeline

[Steve-Pegg]

Optional inclusion of description text inside the rectangles on the timeline.

[mbehr1]

@Steve-Pegg even though the PR is a bit old already, was there any discussion whether this will be supported? I'd like to have this features? Would you mind rebasing it?
@vasturiano or do you mind integrating this feature? (if properly rebased and code-review,... ok?)

[vasturiano]

@mbehr1 thanks for commenting on this.
It's totally fine to integrate this functionality once it's ready. The current implementation is out of sync and touching more surface of the codebase than necessary, so it needs a bit of work before it's ready for merging.