Improved default processor for JST keys

I rewrote the `defaultProcessName` function to be more useful. Currently the filepath is pulled into the JST template keyname, which is not very JS-friendly.

I've improved it by eliminating the filepath (it's still available to an overridden default if someone *really* wants it) and converting filenames to camelCase.

For example: "jade/mega-widget.jade" becomes "megaWidget". Previously, the default key would be "jade/mega-widget", which is cumbersome for lookups.