running futurzize on obspy.core

cmd line arguments:
futurize -0 -w .
py3k utcdatetime: encoding + small neg intergers
py3k utcdatetime rounding workaround
doctest print adjustment utcdatetime
Py3k: casting __radd__, incompatible future int
Py3k refactoring to obspy compatibility module
Py3k compatible attribdict
Py3k: making base and setup.py compatible
Py3k: Increasing compatibility of stream and trace
Py3k: ascii doctests are now compatible
Py3k: compatible test_ascii.py
closing files descriptors: ascii.py, test_ascii.py
avoiding arbitrary order when writing ascii
Py3k: correcting rounding for trim
Py3k: introducing __truediv__ method for trace.py
Py3k: attribdict.py __getattr__ corrected
Py3k converting GSE2 by `futurize -0 -w .`
Py3k: bytes compatibility for gse2

tests libgse2.py and test_libgse2.py pass for 27 and 33
Py3k: bytes compatibility for libgse1

libgse1.py and test_libgse1.py passes
Py3k: tests correcting dynamic imports

using native_str