Added safer path handling for Windows

Fix --include-path option. (typo instead of --include-paths).

The option should be --include-path. You can have multiple
--include-path options though. Add a test where this is the case.

Added DocPad plugin info to README.md

Improve cli tests, fs.exists should be checked after writing the file.

Improve cli, merging node-sass-cli, which includes --watch

Nothing is directly written to stdout/stderr but is passed in an event
emitter, so when testing we can use that.

This way of testing the cli has the advantage that we don't need to exec
for all tests.

- Using node-watch to watch directories or files, exposed with the
  --watch option
- Updated optimist dependency
- Split bin/node-sass into a lib/cli.js and bin/node-sass file, so the
  cli can be required (especially good for testing or extending)

Compiled Win32 - ia32 and x64 precompiled binaries 

Fix includePaths bug

Allow rebuild on Mac

Not sure why, but spawn changes in Node v0.10.x meant that `rebuild.js`
never exited successfully without passing stdio. (#131, #123)

Functionality isn't in the latest libsass