Adds a semicolon to the end of vfs_fonts.js

Adds another grunt task to buildFonts to put a semicolon on the end of vfs_fonts.js after the file gets built.

The missing semicolon was breaking a WIn8 metro app I'm working on.
Merge pull request #160 from ethanova/patch-1

Adds a semicolon to the end of vfs_fonts.js