v0.5.0

This release updates the copy button design and behavior to match GitHub's design guide and button behavior. It also directly inserts the SVG instead of linking it via an <img> tag so that it can be styled more flexibly.

Enhancements

• ENH: Directly add SVG instead of linking via IMG #161 (@choldgraf)
• ENH: Update copybutton image to match GitHub #155 (@choldgraf)