CLN: series to now inherit from NDFrame

Major refactor primarily to make Series inherit from NDFrame
Preserves pickle compat
very few tests were changed (and only for compat on return objects)
a few performance enhancements, a couple of regressions (see bottom)

*obviously this is a large change in terms of the codebase, but it brings more consistency between series/frame/panel (not all of this is there yet, but future changes are much easier)*

*Series is now like Frame in that it has a BlockManager (called SingleBlockManager), which holds a block (of any type we support). This introduced some overhead in doing certain operations, which I spent a lot of time optimizing away, further optimizations will come from cythonizing the core/internals, which should be straightforward at this point*

Highlites below:

  - Refactor of PandasObject to become new generic Pandas base class
    - moved methods
    - __str__,__bytes__,__repr__,save,load 
    - affects all NDFrame hierarchy, Index hierarchy, Period (Timestamp not included) 

  - Refactor of series.py/frame.py/panel.py to move common code to generic.py
    - added _setup_axes to created generic NDFrame structures
    - moved methods

      - from_axes,_wrap_array,axes,ix,shape,empty,swapaxes,transpose,pop
      - __iter__,keys,__contains__,__len__,__neg__,__invert__
      - convert_objects,as_blocks,as_matrix,values
      - __getstate__,__setstate__ (though compat remains in frame/panel)
      - __getattr__,__setattr__
      - _indexed_same,reindex_like,reindex,align,where,mask
      - filter (also added axis argument to selectively filter on a different axis)
      - reindex,reindex_axis (which was the biggest change to make generic)
      - truncate (moved to become part of NDFrame)

    These are API changes which make Panel more consistent with DataFrame
    - swapaxes on a Panel with the same axes specified now return a copy 
    - support attribute access for setting
    - filter supports same api as original DataFrame filter

  - Reindex called with no arguments will now return a copy of the input object

  - Series now inherits from ``NDFrame`` rather than directly from ``ndarray``.
    There are several minor changes that affect the API.

    - numpy functions that do not support the array interface will now
      return ``ndarrays`` rather than series, e.g. ``np.diff`` and ``np.where``
    - ``Series(0.5)`` would previously return the scalar ``0.5``, this is not
      longer supported
    - several methods from frame/series have moved to ``NDFrame``
      (convert_objects,where,mask)
    - ``TimeSeries`` is now an alias for ``Series``. the property ``is_time_series``
      can be used to distinguish (if desired) 

  - Refactor of Sparse objects to use BlockManager

    - Created a new block type in internals, SparseBlock, which can hold multi-dtypes
      and is non-consolidatable. SparseSeries and SparseDataFrame now inherit
      more methods from there hierarchy (Series/DataFrame), and no longer inherit
      from SparseArray (which instead is the object of the SparseBlock)
    - Sparse suite now supports integration with non-sparse data. Non-float sparse
      data is supportable (partially implemented)
    - Operations on sparse structures within DataFrames should preserve sparseness,
      merging type operations will convert to dense (and back to sparse), so might
      be somewhat inefficient
    - enable setitem on SparseSeries for boolean/integer/slices
    - SparsePanels implementation is unchanged (e.g. not using BlockManager, needs work)

  - added ``ftypes`` method to Series/DataFame, similar to ``dtypes``, but indicates
    if the underlying is sparse/dense (as well as the dtype)

Perf changed a bit primarily in groupby where a Series has to be reconstructed in order to be passed to the function (in some cases). the biggest regression is actually a special case and can trivially be changed to be MUCH faster (as this requires a Series for a sum operation), in any event the cython versions are quite fast.

```
-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------
frame_reindex_both_axes                      |  18.8640 |  36.5677 |   0.5159 |
frame_reindex_both_axes_ix                   |  18.7081 |  35.0070 |   0.5344 |
groupby_apply_dict_return                    |  31.2620 |  43.8453 |   0.7130 |
indexing_panel_subset                        |   0.4027 |   0.5000 |   0.8053 |
series_constructor_ndarray                   |   0.0173 |   0.0113 |   1.5352 |
frame_iteritems                              |   3.4393 |   1.8907 |   1.8191 |
frame_fancy_lookup                           |   3.4020 |   1.4997 |   2.2685 |
sparse_frame_constructor                     |  12.0993 |   4.8280 |   2.5061 |
groupby_multi_python                         | 204.1063 |  44.7550 |   4.5605 |
-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------

Target [dfb119d] : PERF: made constructions of SparseFrame have less redundant steps
Base   [67ad556] : Merge pull request #3459 from jreback/GH3455