gyp-only build; submodule removed

The intent behind these changes is to make the module "npm install"able from the git repo url: "git+https://github.com/wdavidw/node-sigar.git" when referenced by another module in package.json.

* Tested only on linux and mac os 10.8.2 so far
* Should re-add submodule once npm does a --recursive clone on dependencies; paths and file contents are
  otherwise untouched

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Let me know if you think I should change something or have a better approach to solving this problem.