Removed unnecessary instruction.
Create separate instruction

I'm not sure if this step is needed, but it existed before. If it is 
needed we should include WHY you have to do this.
Ensure that node is 32bit on win32
Make sure python2.7 is installed on win32

Closes #2193 
Closes #2167
Closes atom/node-runas#5
Remove unnecessary instructions
Update windows build instructions
Require `fs` in bootstrap
Upgrade to grunt-download-atom-shell@0.7.1
Troubleshooting message no longer needed because of 
50a616d91cc5504b9c4daac3156d6ca0598
Merge remote-tracking branch 'origin/master' into cj-windows-build-instructions-update

Conflicts:
	script/bootstrap
Don't require 32bit node
Upgrade to grunt-download-atom-shell@0.7.2
:lipstick:
Move instructions out of requirements
:lipstick:
Merge remote-tracking branch 'origin/master' into cj-windows-build-instructions-update

Conflicts:
	docs/build-instructions/windows.md
Merge pull request #2239 from atom/cj-windows-build-instructions-update

Update windows build instructions and requirements