injection now works even in javascript, but had to add a (hopefully temporary) workaround for https://code.google.com/p/dart/issues/detail?id=16070
added injection into managers
added getter for world to Manager, fix #34
add superclasses for injection to MirrorsUsed
allow addition of components on creation of entity
uniqueId of Entity is no longer 0 for every Entity
setting version to 0.5.2
Merge branch 'release/0.5.2'