Added blocking support for posix

[eranknafo2001]

Fixes #12

[sirhcel]

Thank you for this PR! What about some rewording on the proposed interface: As the I/O operations will always be blocking (in the sense of non-blocking I/O) wouldn't be set_timeout(None) more clearly express "no timeout" than set_blocking(true)?

This would be a breaking change. But couldn't a timeout type with an auto-conversion from Duration like

set_blocking<T: Into<Option<Duration>>>(timeout: T) { ... }

buy us out?

And just as a side-note: Shouldn't be no timeout the default instead of 0? This would at least be my expectation as one who grew up on Linux.

[sirhcel]

This would be a breaking change. But couldn't a timeout type with an auto-conversion from Duration like

set_blocking<T: Into<Option<Duration>>>(timeout: T) { ... }

buy us out?

Giving it a try at Rust Playground, it looks like it could.