Refactor for Package Control

Moved the volt syntax file to the root of the project, as required by
Package Control.
(https://sublime.wbond.net/docs/developers#Creating_a_Package_File)
Removed the .cache file and added it to the .gitignore for the project.
Updated the README.md with the Package Control Information.
Merge branch 'master' of https://github.com/pgtruesdell/volt-sublime-textmate