make slice_order obsolete, replace it with slice_times
reflect Matthew's review
Implement new class for space time realignment. Keep old FmriRealign4d class with deprecation warning
restaure backward API compatibility
improve doc and tests + account for Satra's review
document that `interleaved` kw argument is deprecated in FmriRealign4d
clean docstrings + suppress double warning + PEP8
NF: add python 3 compatibility routines

For future conversion to python 2 / 3 common codebase.
NF+TST: add slicetiming utility functions

Functions for returning slice times given number of slices and TR.

Keep dictionary of allowable names for lookup of function name and
aliases as string.
RF: drafting interface for slice timing.

Make two classes, one for realignment with slice time correction, for
for realignment only.

Simplify options and remove default guess about which is the slice
axis.
RF: move conditional code into if blocks

Timing parameters only used if ``time_interp`` is True; reflect this
with conditional setting of parameters.
NF: raise FutureWarning; check warnings

Raise FutureWarning as well as DeprecationWarning for FmriRealign4d;
check these are raised.
RF: switch tests to use SpaceTimeRealign

Assuming SpaceTimeRealign should be preferred to FmriRealign4d
RF: rewrite example using SpaceTimeRealign
DOC: fixes to timefunc docstrings
RF: delete unused test helper function
fix import error
DOC: clean up typos, formatting; add reference
BF: fix isinstance check to use ndarray

The isinstance check was using np.array as the array class, but the
class is np.ndarray