Fixed composer configuration
Renamed ReadableContainerInterface to ContainerInterface
#3 Added ContainerException, NotFoundException extends it
Merge pull request #9 from container-interop/ContainerException

Base ContainerException
Updated README with more introductory text.
Merge pull request #12 from jeremeamia/feature/update-readme

Updated README with more introductory text.
Updated to PSR-4.
Merge pull request #11 from jeremeamia/feature/psr4

Updated to PSR-4.
Merging from new master