Add concurrent package validation

[willirath]

• Use multiprocessing from the std lib to concurrently validate packages. Add a cli argument num-threads setting the number of concurrent processes to be used.

• Add test for three concurrent scenarios: num_threads=0 using all available cores, num_threads=1 for serial validation, num_threads=4 explicitly using four processes.

• Adapt Travis script to properly measure test coverage with concurrent validation.

This is a cleaned-up version of #45.

[codecov[bot]]

Codecov Report

Merging #48 into master will increase coverage by 0.47%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
+ Coverage   94.06%   94.53%   +0.47%     
==========================================
  Files           2        2              
  Lines         219      238      +19     
==========================================
+ Hits          206      225      +19     
  Misses         13       13

Impacted Files	Coverage Δ
conda_mirror/conda_mirror.py	94.46% <100%> (+0.48%)	:arrow_up:

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[ericdill]

works locally. Thanks @willirath ! Merging, tagging and deploying a new version to pypi/conda-forge

[jhoblitt]

Outstanding! :+1:

[ericdill]

should be able to pip install 0.7.0 which has the additional command line flag --num-threads that allows you to do concurrent package validation.

[ericdill]

conda package for 0.7.0 should be available in the next week or so.