add @kaeufl to credits, see #724
avoiding future dependency in setup.py

problem was imported obspy.core.version.

Probably we can get rid of most from future.builtins import open
lines...

see #730
Trying to resolve sphinx build failures

seems like for older versions of numpy mode must not be unicode, forcing
native string.

Failure were:
* http://tests.obspy.org/12773/#15
* http://tests.obspy.org/12773/#16
fixing some doctests in fsdn.client

* http://tests.obspy.org/12773/#9
* http://tests.obspy.org/12773/#10
Merge branch 'releases' of https://github.com/obspy/obspy
clear message if numpy is missing at install time. closes #730
Merge remote-tracking branch 'upstream/releases'
Correcting docs (based on sphinx output)

see #725 and http://docs.obspy.org/master/log.txt