add failing test for processing that is passed to scipy done on empty traces
new decorator to skip processing for empty traces
skip (scipy) processing for empty traces (which raises otherwise, usually with something
like IndexError)
Merge remote-tracking branch 'upstream/master' into skip_scipy_for_empty_traces
Merge branch 'master' into skip_scipy_for_empty_traces

Conflicts:
	obspy/core/tests/test_trace.py
	obspy/core/trace.py
	obspy/core/util/decorator.py
Merge pull request #636 from megies/skip_scipy_for_empty_traces

Skip scipy for empty traces