Add windows support

[JoeyAcc]

I'm assuming that the main reason that there currently is no windows support for liner is that the termion dependency has no windows support either.

However, there is an open issue here to add that functionality.
Once that is merged, It would be great if windows support could be added here as well.

I have a liner fork here that uses a termion fork in order to add this support. I haven't turned it into a PR because I think some more work may be necessary. For example, it seems to work fine on the windows CMD shell, but starting my application using the git Bash shell results in an infinite list of:

[Err] Error { repr: Custom(Custom { kind: Other, error: StringError("Unable to get the terminal size.") }) }

However, it can easily be tested in a project using liner by using my github fork as a dependency:

liner = { git = "https://github.com/jjpe/liner", branch = "windows" }