Verbose required paths

I installed to `c:\nodejs` to avoid spaces in path (old habits die hard). So i had an obstacle you see.
Travis says `line too long`

80 chars limit hit
Paul says `lookup PATH`

Works both with trailing slash `c:\nodejs\` and without it `c:\nodejs`
WINDOWS_NODE_PATHs are to stay

WINDOWS_NODE_PATHs are checked first, and then os.environ['PATH']
Compose full list in one place
Preserve that empty line
Paul suggests paths to be reversed
Merge pull request #864 from IgorKlopov/patch-1

Lookup node in PATHs