herokuJdkVersion 1.7 also failed...

```
2014-11-01T15:56:55.175655+00:00 app[web.1]: java.lang.UnsupportedClassVersionError: sun/security/ec/SunEC : Unsupported major.minor version 52.0
2014-11-01T15:56:55.175658+00:00 app[web.1]: 	at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
```

...trying 1.6.