Make YAML optional

validate composer
Add composer installation instructions to each package. Closes #13
Kickstart a travis build
Tweak usage of Symfony YAML
Merge pull request #166 from dongilbert/installation

Add composer installation instructions to each package. Closes #13
Merge branch 'yaml-tweak' of https://github.com/fabpot/joomla-framework into JRegistryFormatYaml
Clean up code style. Update tests.
Merge pull request #165 from dongilbert/JRegistryFormatYaml

Make YAML optional
Add testing for SqliteDriver
Additional database testing + bug fixes

- Expand database coverage on MySQL(i) and SQLite drivers
- Modify MysqliDriver::getCollation() to not depend on a specific table
- DatabaseDriver::getConnectors() not returning connectors