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ARROW-3369: [Packaging] Wheel builds are failing due to wheel 0.32 release

Wheel builds: https://github.com/kszucs/crossbow/branches/all?utf8=%E2%9C%93&query=build-324

- Updated numpy version
- Pinned multibuild version
- Pinned wheel version to `0.31.1` until auditwheel and multibuild compatibility issues are resolved

Author: Krisztián Szűcs <szucs.krisztian@gmail.com>

Closes #2661 from kszucs/ARROW-3369 and squashes the following commits:

fdb1e96a <Krisztián Szűcs> todo note
64273b45 <Krisztián Szűcs>  pin wheel after installing tensorflow
3f7b8f18 <Krisztián Szűcs> organize env vars
246f3143 <Krisztián Szűcs> install osx wheel build dependencies
ab130a74 <Krisztián Szűcs> fix pip version pin
c946b0f1 <Krisztián Szűcs> pin wheel version for osx and linux builds