Modernize PHP port of User Agent Parser

Bring User Agent Parser to the year 2013.

- [x] Use composer for dependency management
- [x] Introduce namespaces
- [x] Removing legacy library dependencies
- [x] Use PHPUnit for testing
- [x] Make all tests pass, fix all the remaining bugs
- [x] Introduce specific result objects
- [x] Comply with PSR-X coding standards
- [x] Use Travis for CI
- [x] Update README
- [x] Port command line tool to Symfony CLI
- [x] Secure updating: SSL certificate verification, hashing, try to do atomic updates
-  [x] Restore fetching YAML file only (without generating JSON)