Version 0.7.0

This release fixes several bugs in isal_zlib. It now is a proper drop-in
replacement for zlib. This is a major milestone towards the 1.0.0
release.

• Remove workarounds in the igzip module for the unconsumed_tail
  and unused_data bugs. igzip._IGzipReader now functions the same
  as gzip._GzipReader with only a few calls replaced with isal_zlib
  calls for speed.
• Correctly implement unused_data and unconsumed_tail on
  isal_zlib.Decompress objects.
  It works the same as in CPython's zlib now.
• Correctly implement flush implementation on isal_zlib.Compress and
  isal_zlib.Decompress objects.
  It works the same as in CPython's zlib now.