v0.5.0

Changelog:

• #67, #69 - Default SASS variables (allow variables to be overridden)
• #62 - Adding up-left, up-right, down-left, down-right positions.
• #61 - Fixing iOS Safari bug where tooltips doesn't showed up on click
• #53 - Adding no-transition parameter [data-balloon-blunt]
• Other minor bugfixes...