nicer question mark prefix

### OS X

![screen shot 2014-08-15 at 19 12 28](https://cloud.githubusercontent.com/assets/170270/3936501/59ebe532-24a2-11e4-96ee-f42240419f0e.png)

### Windows

![screen shot 2014-08-15 at 19 18 23](https://cloud.githubusercontent.com/assets/170270/3936500/59e8c550-24a2-11e4-9606-b4d485c29def.png)

### Linux

![screen shot 2014-08-15 at 19 19 57](https://cloud.githubusercontent.com/assets/170270/3936499/59e6ec80-24a2-11e4-99bd-a6e543b1d17c.png)


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Existing prefix (OS X):

![screen shot 2014-08-15 at 19 35 20](https://cloud.githubusercontent.com/assets/170270/3936519/92cb1774-24a2-11e4-9568-b98830096e7c.png)