[CI] repo.continuum.io can be flaky in builds

[asfimport]

I have seen this flakiness in several builds:

++wget --no-verbose -O miniconda.sh https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh
wget: unable to resolve host address ‘repo.continuum.ioâ€

e.g. https://travis-ci.org/apache/arrow/jobs/410201987

Reporter: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #2349

_{Note: This issue was originally created as ARROW-2949. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 2349
#2349