Changes to manual

- I clarified on the mission statement for EAK. It now conveys our intention that ember-cli will one day take over.
- Turned the praise for grunt down a notch :)
- Added an overview of when to use dashes and when to use camelCase (From https://github.com/stefanpenner/ember-app-kit/pull/501)

@stefanpenner What do you mean with https://github.com/stefanpenner/ember-app-kit/blame/gh-pages/guides/naming-conventions.md#L93 ? The is no underscore oO