Merge pull request #2958 from jreback/timedelta_2957_new

BUG: fixed .abs on Series with a timedelta (partial fix for 2957)
ENH: add .loc attribute to provide location-based indexing

TST: added multi-index tests

DOC: changed loc -> iloc
     added more docs

ENH: added integer lists as indexers to iloc

ENH: raise correctly on out-of-bounds slicing
     support negative indexing in iloc and icol

CLN: move all indexings (ix/iloc) to PandasObject in generic.py
     (except _SeriesIndexer in series.py)
     add name parameter to Indexer creation, makes indexers independent
     of their external names
TST: new test suite for indexing
ENH: added loc/at/iat indexers ....almost done
DOC/TST: revised indexing section in docs
         updated whatsnew
         all tests work

DOC: changes suggested by Jan Schulz
     revised whatsnew to include mostly references to new indexing
DOC: added 10min newbie intro to pandas
     changes in indexing suggested by Jan Schulz, and nehalecky

DOC: added plotting,reshaping, more examples in setting to 10min.rst

DOC: more doc updates, added more examples in selection
     added join to 10min

DOC: release notes and whatsnew updates for 10min
DOC: revamped dtypes section in basics.rst
     fixed removal of foo temp files in 10min

DOC: added to time series in 10min.rst
DOC: added sorting examples to 10min
BUG: fixed multi-index selection via loc, back to using some
     of ix code (but still do validation if not mi)

ENH: add xs to Series for compatiblity, create _xs functions in all objects
DOC: added several sub-sections to 10min
     fixed some references in basics.rst