fix(config): config name should be camel case

When you `observe` a config value, it will be added into the `atom.config` and it not seems to be a good behavior to have not camel case config name.

![screen shot 2014-05-30 at 3 21 15 pm](https://cloud.githubusercontent.com/assets/893837/3130914/89d62478-e7fe-11e3-8944-e8efb58cdd11.png)

The issue #64 is affiliated I think.