Throwing Aura exception on ReflectionException

When ReflectionClassa fails a ReflectionException is thrown. Config
object should fetch it and rethrow as Aura\DI\Exception thus
encapsulating external exceptions.
throw exception when setter does not exist; thanks @MAXakaWIZARD.
Merge branch 'develop' of github.com:auraphp/Aura.Di into develop
Merge pull request #22 from alwynn/reflection-exception

Throwing Aura exception on ReflectionException
rename ServiceInvalid to ServiceNotObject, to indicate what exactly is invalid; use new ReflectionFailure exception in place of old ServiceInvalid; add some 'use' statements
actuall add the exception file
add travis build status badge
update license
update meta
update docblocks:
remove unused exceptions
update changes