Switches from CodeKit to Grunt for automation.

Also makes the switch from Less to Sass.

Fixes #13, #20
Fixes some themes adding borders and changing font sizes.

Fixes #19
Updates Grunt configuration.
Adds plugin auto updating capabilities via GitHub Updater.

Fixes #24
Updates version number and copyright date.
Adds comment if shortcode is used incorrectly.

Fixes #28
Adds check to see if content uses the shortcode.

Fixes #27
Changes plugin shortcode.

Fixes #26
Cleans up database on uninstall.

Fixes #30
Adds support for id shortcode attribute.

Fixes #25
Updates README with detailed contribution instructions.
Merge pull request #33 from manovotny/3.0.0-release

3.0.0 Release