Fixed windows-specific problem in subprocess_repl.read_bytes()

Fixed windows-specific problem in subprocess_repl.read_bytes(), so that more than 1 byte is returned on every read, by converting the pipe to an asynchronous one.

This issue comes up as a bug at some places, for example open an ipython repl prompt, then enter some non-existent variable name to generate an error. Then the color escape sequences are not stripped even when the option is set to True in SublimeREPL, as the color stripping function only has a single byte as input instead of all the output bytes.

This fixes the aforementioned problem.