0.3 Stable version

Major changes: * Released MineRLObtainDiamondVectorObf-v0 (and other obfuscated environments for the competition! See http://minerl.io/) * Released new V3 dataset containing both obfuscated and standard env data. * Internally refactored the MineRL API to use env handlers. * Unified the data publishing and environment specification API * Forced all spaces to return Numpy arrays and scalars. * Open sourced the data publishing pipeline * Added forbidden streams to the data pipeline * Rewrote the MineRL viewer to be extensible and support rendering for competition streams * Rehosted the data on S3, drastically increasing * Made Asia and Europe mirrors for the dataset. * Made new MineRL download method (supports sharding and mirrors)