Use `url.resolve` instead of `path` if url has protocol (e.g. http://)

In order to optimize remote modules, I attempted to use the url which has protocol as `baseUrl` (e.g. `http://url/to/base`), but I couldn't do it. The issue seems to be caused by the thing that `path.join('http://url/to', 'hello.js')` returns `http:/url/to/hello.js` (not starts with http://), and also `path.relative` do it like that. So the changes use the `url.resolve` function instead of `path.join` / `path.relative` if the baseUrl has protocol.

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* `index.js`: Add `hasProtocol` function
* `package.json`: Add connect module into devDependencies
* `test/url.js`: Add a test to check url which has protocol
  * (copy the most of test/basic.js)
* `test/utils/loadFileFromNet.js`: Add `loadFileFromNet` function to load module through http
  * (copy the most of test/utils/loadFile.js)

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Thanks,