Updated pullquote icon for articles

Before:
![screen shot 2014-10-22 at 14 26 17](https://cloud.githubusercontent.com/assets/2236852/4736803/0062e8b6-59f0-11e4-997e-858572cefdf5.png)


After:
![screen shot 2014-10-22 at 14 26 00](https://cloud.githubusercontent.com/assets/2236852/4736805/04238b40-59f0-11e4-9ae7-8c688eea6935.png)