Updated link to issue #249 in obspy.signal.cross_correlation.xcorr
docstring.
Partially fixes #513.
Added offset and kurtosis code and tests
Added forgotten test for offset
Cleanup to reduce number of changed lines
Added Chassande-Mottin reference
Added full reference for kurtosis implementation
Merge pull request #516 from claudiodsf/513

Updated link to issue #249 in obspy.signal.cross_correlation.xcorr docstring.
Updated citation to run pybtex correctly
adapting citation
removing unnecessary setup.cfg
changelog and credits update
Merge pull request #517 from amaggi/am-realtime

Some new real-time functions