Entity uses long for id
PooledEntity correctly sets its id to 0 on reset
Changed getIndex() to getId()
Adds getEntities() to IntervalIteratingSystems and IteratingSystem for issue #71
Fixes GWT compatibility issue #73
Fixes comment in entity id
Renames id to uuid
Ups version to 1.3.0 pre-release
Ups version to 1.3.1 post release
Fixes Family hashing issue #78
Fix #77 where attempt to remove a Component from an
already-reset PooledEntity would cause an IllegalArgumentException.
Adding a SortedIteratingSystem and unit tests