Add three new themes, make installable

Merge pull request #19 from HubSpot/install

First pass at making Shepherd installable

v0.5.1

Fixes a bug in how events get propagated to the global Shepherd object.

v0.5.0

• Reverses the top and bottom attachment keywords, to make things consistent
• New active and inactive events are fired when a tour begins and ends. These events are also propagated to the global Shepherd object.
• New showCancelLink option, which shows an '×' link in the header of the step.
• New data attribute data-shepherd-step is added to the body during the tour.
• New class on the body shepherd-active when a tour is under weigh.

Remove font size inheritance from `shepherd-theme-arrows-plain-buttons`

v0.4.7

Remove font size inheritance from `shepherd-theme-arrows-plain-buttons`

Arrows plain buttons theme

v0.4.5

Bump

v0.2.0

v0.2.0