Fix exercise links in scatter coach report 

Fix for #1899

Basically, links to individual exercises weren't available because we weren't passing in exercise meta data. Now we are, and it seems to work. Bonus feature includes also seeing the full name of the exercise instead of the slug. 

![image](https://cloud.githubusercontent.com/assets/1319950/2647302/0f01ac78-bf49-11e3-9cf4-8af76a74e96d.png)

After exploring the coach reports for the first time, I found some things that could use a bit of polish. Going to list some here off top of head and create issues soon:

* Modal instead of tooltips (so they don't hang off the page and we can use more space)
* Only meaningful options available for select boxes (too much choice) 
* Selecting from topic tree should be have more helpful info 
* Think through coloring of legends / information we are trying to convey with each report, try to think of ways to make it as meaningful as possible (same as second option)