BUG: Fix wrong str.format() calls in Index.summary

GH3869
Merge pull request #4751 from jtratner/fix-summary-GH3869

BUG: Fix wrong str.format() calls in Index.summary
BUG: Fix crash using to_csv with QUOTE_NONE

Now passes `quotechar` to csv's writer. Default is same as csv (`'"'`),
but sets to `None` with `quoting=csv.QUOTE_NONE`.
Merge pull request #4752 from jtratner/fix-to_csv_QUOTE_NONE-GH4328

BUG: Fix crash using to_csv with QUOTE_NONE
ENH:  GH2578, allow ix and friends to partially set when the key is not contained
      in the object
API: iat/iloc will raise if enlargement is specified as its ambiguous

CLN: set_value in Series/Frame now go thru indexing routings in core/indexing.py
Merge pull request #4515 from jreback/partial_setting

ENH/API:  GH2578, allow ix and friends to partially set when the key is not contained in the object