Update Tether to v1.0.0

Merge pull request #70 from HubSpot/tether-v1

Update Tether to v1.0.0

Major release

• Proper UMD
• Update build process
• Coffeescript -> ES6
• Remove bundled version
• Contributing and Changelog
• Bump to v1.0.0

Remove Compass and Ruby dependencies

Remove Compass (and therefore Ruby) dependency to make contribution to the project easier.

Add promise option before showing step

v0.7.1

Bump version

Add before-show and before-hide events

v0.7.0

Bump version

v0.6.14

Bump version

v0.6.13

Release

v0.6.12

Add square dark theme

v0.6.11

Typos

v0.6.8

Build for release