Move conda build and ASV check to cron job

[TomAugspurger]

xref #19695 (not closing until pip build test is moved or we decide to keep that here)

https://travis-ci.org/pandas-dev/pandas-ci and http://github.com/pandas-dev/pandas-ci

[TomAugspurger]

https://travis-ci.org/pandas-dev/pandas-ci is passing now and set to run daily.

Will merge this once travis passes.

[codecov]

Codecov Report

Merging #19698 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #19698      +/-   ##
==========================================
+ Coverage   91.58%    91.6%   +0.02%     
==========================================
  Files         150      150              
  Lines       48867    48867              
==========================================
+ Hits        44755    44767      +12     
+ Misses       4112     4100      -12

Flag	Coverage Δ
#multiple	89.98% <ø> (+0.02%)	⬆️
#single	41.75% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/plotting/_converter.py	66.95% <0%> (+1.73%)	⬆️

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[TomAugspurger]

FYI, I renamed 3.5_CONDA_BUILD to 3.5 and removed the 3.6_ASV job entirely.

[TomAugspurger]

OK, this is all green other than the pip failure from #19668 (looking further into that later today hopefully) https://travis-ci.org/pandas-dev/pandas/builds/341580276

Thoughts on adding --skip-network to the "2.7" build? It's the slowest by ~15 minutes. We'll want to make sure at least one of the 2.7 builds has the flag.

FYI, this weekend I'm planning on revamping some of this stuff into a more declarative YAML form. Then we can have a small script that parses those and prints out which builds have which flags / pinned deps.