[Python] Use RecordBatch.from_pandas in FeatherWriter.write

[asfimport]

In addition to making the implementation simpler, we will also benefit from multithreaded conversions, so faster write speeds

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #1250

_{Note: This issue was originally created as ARROW-1675. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Resolved by PR 238881f