[Python] Manylinux1 builds timing out in Travis CI

[asfimport]

Not sure why this is happening – I think the docker pull has been a lot slower of late

Reporter: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-3271. Please see the migration documentation for further details.}

[asfimport]

Uwe Korn / @xhochy:
We could limit the manylinux1 builds to e.g. a single Python version to improve the build times. They are quite important as they are the lower bound in the compiler versions that we support.

[asfimport]

Wes McKinney / @wesm:
This seems to have been a transient problem