Add Code Climate badge

Code Climate is in the testing phase for ES6 parser support and we've upgraded this repo to take advantage of that.

### Statistics
1. 281 new files are being analyzed with the following GPA breakdown:
  * **A**: 261
  * **B**: 8
  * **C**: 14
  * **D**: 16
  * **F**: 8
2. `19,097` new lines of JS code are being analyzed
3. GPA average increased from `0.40` to `2.85`

We're always working towards improving our analysis. Please let me know if you have any questions.