Log Message:
Update ruby-sprockets to 3.3.4.

**3.3.4** (September 1, 2015)

* Relative cache contents now work with windows.

**3.3.3** (August 21, 2015)

* Remove more absolute paths from cache contents.

**3.3.2** (August 19, 2015)

* Fix cache contents to use relative paths instead of absolute paths.

**3.3.1** (August 15, 2015)

* Fix legacy Tilt integration when locals is required argument.

**3.3.0** (August 12, 2015)

* Change internal cache lookup to use relative asset paths instead of absolute paths.