Exclude more unneeded files in dist builds

This Gruntfile excludes way more unnecessary files (mostly `test/`, `doc/` and `examples/`), which results in a dist folder taking up way less space than before (resulting in a smaller installer).

Disk space usage analysis (using RidNacs):
On `master`:
![image](https://cloud.githubusercontent.com/assets/2641501/5491879/ee2307ca-86dc-11e4-9322-3fb9d1fedd81.png)

On `dist-exclude`:
![image](https://cloud.githubusercontent.com/assets/2641501/5491885/f953071c-86dc-11e4-9b29-88ec1c1893e0.png)

I haven't tested this at all, though.