NF: TransposeMapper
NF: AddAxisMapper for more elegant dataset aggregation.
BF: Although it costs something: Mappers promise a new dataset

Transpose cannot be an exception from the rule the forward() produces an
independent dataset object.
BF: _str() arguments need to by strings, and only that
Merge remote-tracking branch 'gh-master/master'

* gh-master/master: (24 commits)
  BF: adjusting ttest_1samp code and test to pass on older numpy/scipy's
  BF: removed unneeded import * from  a test function
  ENH: reimplement/renamed ttest_1samp{_masked,} using np.ma
  NF: ttest_1samp_masked for running t-test with some masked data (+arbitrary tail)
  TEST: make test robust on old numpy/python's
  TEST: apparently scipy.fit on squeeze lacks ability to freeze any parameter
  BF: provide explicit key for sorting distribution matches tuples
  BF: monkey patch scipy with broken fit for 2 fixed params (e.g. floc and fscale)
  BF: match_distributino - use "resolved" dist_gen, which might original be a tuple
  BF: workaround for sphinx -- import Process as private __Process from psutil
  BF: fix legend in plot match distributions
  ENH: suppress Python warnings while match_distribution
  ENH/BF: compute unique only if not known + handle all obscure cases via ndarray(list(set()))
  ENH: just an additional externals check to see if np.unique is flawed
  BF: h5py external is required for results_backend="hdf5"
  ENH: run unittest-py3 for origin/master and tiziano/master +store output for examples +safe guard WTF call
  PY3: make SequenceCollectable.unique faster.
  BF: assure different filenames in the SL's _proc_block by providing index of the block (should fix gh 87)
  ENH: make h5py version available
  BF: hdf5 -- flatten and save attr 'shape' for object ndarrays (Closes gh-84)
  ...
ENH: sl -- make _sl_call and _proc_block just return results

roi_sizes now handled similarly to as roi_features_ids before -- by
storing them in results.a
ENH: SL -- results_fx and nblocks to allow "on-the-fly" processing of results

with nblocks >> nproc and custom results_fx it becomes feasible to
work on problems where storing all searchlight results in memory and
post-processing them all at once is prohibitive due to large memory
requirements.

with this modification input is split into larger number of smaller
feature "partitions", results spit out by a generator which is passed
to results_fx making it possible to process them "on-the-fly" and
dumping them right after thus not requiring as much memory.
ENH: SL -- move hstacking and assignment of .ca's into _concat_results

it was correct course of action anyways since hstacking might not be needed
or produced results would not carry needed .a's -- so they better be handled
by the custom results_fx when pristine results are available
ENH: robustify the test to handle when results are wrapped into a dataset
Merge pull request #88 from hanke/shape_mappers

Shape mappers
Merge pull request #92 from yarikoptic/_tent/sl_nblocks

 ENH: SL -- results_fx and nblocks to allow "on-the-fly" processing of results
DOC: Commit unfinished multiclass tutorial.
Merge remote-tracking branch 'gh-master/master'

* gh-master/master:
  ENH: robustify the test to handle when results are wrapped into a dataset
  ENH: SL -- move hstacking and assignment of .ca's into _concat_results
  ENH: SL -- results_fx and nblocks to allow "on-the-fly" processing of results
  ENH: sl -- make _sl_call and _proc_block just return results
  BF: Although it costs something: Mappers promise a new dataset
  NF: AddAxisMapper for more elegant dataset aggregation.
  NF: TransposeMapper
Fixing url to the issue tracker (Closes gh-93) (Thanks channingmoore)