Improve build times

_Ignore the branch name, I was going to use JIT and realized that task loading isn't the problem, it's running all of those Topdoc tasks._

- Adds the timer-grunt task so we can measure improvements.
- Adds the grunt-concurrent task to run all Topdoc tasks concurrently reducing the `grunt` build time from 12.7s to 4.8s.

Before:
![screen shot 2014-09-04 at 10 16 55 am](https://cloud.githubusercontent.com/assets/1093373/4151753/cdd24fb2-3448-11e4-9280-8f1e9754002f.png)

After:
![screen shot 2014-09-04 at 11 29 36 am](https://cloud.githubusercontent.com/assets/1093373/4151758/d3624752-3448-11e4-975c-e326be207979.png)


We could try to do more things concurrently but I think the messiness of setting it up will outweigh the small gains we will get. We should try grunt-newer next and see how low that gets us.