Make Former framework-agnostic

# Not actually up to date, things work actually better than this

- [x] Abstract Former's app dependency
- [x] Merge the `legacy`, `composer` and `agnostic` branches
 
### Laravel 3

- [x] Static facade
- [x] Markup
- [x] Populating
- [x] Repopulating
- [ ] Custom configuration file
- [ ] Localization
- [ ] Errors handling
- [ ] Live validation

### Laravel 4

- [x] Static facade
- [x] Markup
- [x] Populating
- [x] Repopulating
- [ ] Custom configuration file
- [ ] Localization
- [ ] Errors handling
- [ ] Live validation

### Stand-alone

- [x] Static facade
- [x] Markup
- [x] Populating
- [ ] Repopulating
- [ ] Custom configuration file
- [ ] Localization
- [ ] Errors handling
- [ ] Live validation