Loosens limitations on naming partials/filters.

At the moment reserved tokens will not be added to partial or filter
names meaning you could not do the following:

``` javascript
var tmpl = combyne("{%partial partials/test%}");
tmpl.registerPartial("partials/test", combyne("Hello world"));
```

An error would pop up saying unexpected token PARTIAL.  In my opinion, I
designed this too strictly and it should be changed to allow for any
variety of characters.