Fix #2102: set 72dp left content inset

Fix #2102: set 72dp left content inset.

Looks better on Comments and Notifications screens:
![screen shot 2014-12-15 at 15 33 00](https://cloud.githubusercontent.com/assets/40213/5437661/44b1e9ca-8472-11e4-8f98-cba25da7a6ee.png)

We should maybe remove padding in `reader_spinner_item.xml` for a better effect:

![screen shot 2014-12-15 at 15 34 49](https://cloud.githubusercontent.com/assets/40213/5437672/514f2b3e-8472-11e4-9b27-51d8fb7c9dec.png)