Windows fix

[bkmartinjr]

Changes all related to Windows port:

• Fixes for issues windows: incorrect split between high and low for position and offset #5 and issue windows: always creating paging mapping, not file mapping #6. Tested on Win10/Node 8.9.1 and Win10/Electron 1.8.3beta.3
• Updated package.json to stop using a deprecated 'prepublish' script name (see https://docs.npmjs.com/misc/scripts#deprecation-note)
• skip tests which will aways fail on Windows due to OS behavior (see comment in test.ls)
• added missing stub for mincore() on Windows and better error checking in common code

Note that fixing issue #6 requires a relatively new Node version. For details see nodejs/node#6369 and libuv/libuv#1291

[ozra]

Thanks, I'll have a look tomorrow before the holiday craze continues :)

[ozra]

Sorry to keep you waiting.
I'd prefer PR's on their own feature/fix branches, however I'll just merge and cleanup locally. I'll seek to clarify the information under the contribution header in the README.
Thanks a lot for the fixes!