Make the action ready

[aminya]

For atom#2459

• Fixes the conflicts by merging upstream/master into this branch
• Adds windows to the CI
• Adds visualcpp-build-tools 2015 on Windows
• Runs the tests on Windows (continuing on errors for now)
• Run the CI on beta too: Sometimes Github goes into the beta channel. In addition, that also helps to catch the bugs of beta before it reaches stable.

[codecov]

Codecov Report

Merging #9 (d177860) into master (875415a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@ Coverage Diff @@## master #9 +/- ##
==========================================
+ Coverage 93.42% 93.46% +0.03% 
==========================================
Files 236 237 +1 Lines 13196 13234 +38 Branches 1897 1906 +9 ==========================================
+ Hits 12329 12369 +40 + Misses 867 865 -2 

Impacted Files	Coverage Δ
lib/views/git-identity-view.js	100.00% <ø> (ø)
lib/views/git-tab-view.js	86.95% <ø> (ø)
lib/containers/github-tab-container.js	100.00% <100.00%> (+3.33%)	⬆️
lib/containers/github-tab-header-container.js	100.00% <100.00%> (ø)
lib/containers/remote-container.js	100.00% <100.00%> (ø)
lib/controllers/editor-conflict-controller.js	100.00% <100.00%> (ø)
lib/controllers/git-tab-controller.js	86.61% <100.00%> (+0.90%)	⬆️
lib/controllers/github-tab-controller.js	100.00% <100.00%> (ø)
lib/controllers/remote-controller.js	100.00% <100.00%> (ø)
lib/git-shell-out-strategy.js	99.81% <100.00%> (ø)
... and 13 more

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