Parse MiniSEED packets for INFO requests.

This enables reading INFO request responses from the IRIS ringserver.

(Previously the MiniSEED payload was simply guessed to start at 8 bytes
offset.)
Fixed use of builtin as variable name.
PEP8
fixes 2038 problem (see #805)
extra test case for #805
reuse TIMESTAMP0 constant
fixes 2038 problem (see #805)
Conflicts:
	obspy/core/tests/test_utcdatetime.py
	obspy/core/utcdatetime.py
extra test case for #805
reuse TIMESTAMP0 constant
changelog
Merge branch 'releases'

Conflicts:
	CHANGELOG.txt
	obspy/core/utcdatetime.py
Added unittest for different MiniSEED packets.
Added correct ticket number.
__ne__() for Catalog objects.
Python 3 compatibility
Flake8

(Sorry.)
Merge pull request #807 from bmorg/fix_seedlink_miniseed_parsing

Use clibmseed to parse INFO responses in MiniSEED
minor docstring fix (see #808)
Use faster pcolormesh for plotting PPSD.
Changelog.

Changelog for 51e593d44282200824e823a4f3890c435afcce94.