quake ML validation using relaxNG schema

- validation now actually meaningful ;)
- two minor modifications from current official QuakeML 1.2 relax NG
- deactivating default stdout printing in validate routine, I would not
  expect a basic check routine that returns True/False to print messages
adapt two tests to be valid QuakeML
workaround for #559
changelog for quakeml validation
Better error msg for test_writeAndReadDiff...()

Eases debugging.
Fixing confusion of numpy.string_ dtypes.

test_writeAndReadDifferentEncodings() now works across different NumPy
versions. Fixes #552.
PEP8 for obspy.mseed
Merge pull request #560 from megies/quakeml_validation

Quakeml validation
signal, template cross correlation: handling some edge cases
seishub client getKML: handle events w/o lat/lon
Slight reordering during QuakeML writing.

Assures that no empty file gets written if the validation fails. Also
passed open files will now remain open. The function only closes file
handlers it also opened.
Changes to the regex used to validate publicIDs.

It now correctly validates the URIs. It was too permissive before.
Update DEPENDENCIES.txt

pinning pep8 and coverage - newer versions won't work
all public C methods need to be listed in .def file for win
fixing a failing import
pep8
minor docstring change
fixing iris test case
fixing various arclink test cases
Merge branch 'master' of https://github.com/obspy/obspy