TST: Adjust boxplot tests following MPL API change

fliers on a boxplot are now 1 object instead of 2.
DOC: mention 'category' in select_dtypes docstring
Merge pull request #8439 from bthyreau/doc_selectdtypes_categ

DOC: mention 'category' in select_dtypes docstring
BUG: NDFrame.equals gives false negatives with dtype=object (GH8437)
Merge pull request #8443 from unutbu/dtypeO-equals

BUG: NDFrame.equals gives false negatives with dtype=object (GH8437)
CI: use conda for most build dependencies
Merge pull request #7971 from cpcloud/conda

CI/WIP: Use conda for most deps
BUG: bug in df.info() when embedded categorical (related GH7619)
Merge pull request #8449 from jreback/cat

BUG: bug in df.info() when embedded categorical (related GH7619)
Remove DataFrame.delevel
Merge pull request #8451 from jsexauer/fix_delevel

Remove DataFrame.delevel
BUG: reset identity on legacy index pickles (GH8431)
Merge pull request #8454 from jreback/legacy_pickle

BUG: reset identity on legacy index pickles (GH8431)
DOC/CLN: Cleanups plotting.py
PERF: Improve performance of CustomBusinessDay
API: SQL class definitions renaming

- renaming of PandasSQLAlchemy to SQLDatabase and PandasSQLTable to SQLTable
- renaming of SQLDatabase.read_sql to read_query (to be consistent with read_query/read_table)
- legacy -> fallback
TST: compat for *.pkl -> *.pickle in pandas/tests/data
PEP8 fixups
Merge pull request #8293 from bjonen/fix_8236_2

PERF: Improve performance CustmBusinessDay - 2nd
TST: fix path for getting pickles wrt (GH8431)