Commits
Krisztián Szűcs authored and Wes McKinney committed 72598e4980e
ARROW-3766: [Python] pa.Table.from_pandas doesn't use schema ordering
Author: Krisztián Szűcs <szucs.krisztian@gmail.com>
Closes #2979 from kszucs/ARROW-3766 and squashes the following commits:
7038e92d6 <Krisztián Szűcs> initialize dataframes from OrderedDict
5480e3d7c <Krisztián Szűcs> remove __index_level_{}__ fields from subschema in parquet write_to_dataset
e93d770ea <Krisztián Szűcs> py2 compatibility
8d27a9d42 <Krisztián Szűcs> adjust test case
d1185fe98 <Krisztián Szűcs> make schema and columns arguments mutually exclusive
950f3b8f3 <Krisztián Szűcs> Table.from_pandas keep column ordering