Parametrize Editor by the Completer type

This allows the `Editor` to implement `Sync` as long as it contains a completer which implement `Sync`. It lets the `Editor` take ownership of the completer.

Make History ignore space/dups configurable (#50)

Adding basic windows support

And declare target specific dependencies.

Accidently added history.txt to repo, remove from repo and add it to the
gitignore

Building and testing all the different windows environments against
stable/beta/nightly would take too long.  Reducing the environments msvc &
gnu 64 bit environments for beta and 1.9.0 rust

* get_columns
* is_a_tty
* enable_raw_mode
* disable_raw_mode
* Drop trait for WindowsTerminal struct

libc does not define the STDIN_FILENO & STDOUT_FILENO for the windows
platform.  We instead check whether or not stdin and stdout are TTY
by checking the GetConsoleMode output.

Instead of using custom path to module in lib.rs, load modules for different tty
platforms in tty/mod.rs

Terminal trait is defined in tty/common.rs where it requires
implementation of enable_raw_mode and disable_raw_mode.  readline_edit
will now move around a mutable reference to a Terminal instead of the
platform specific struct.

This reverts commit 715f658e4900cfd9a8c8f0f54a3a5cdc89c25363.

In order to support the windows platform, we will split the platform
specific logic into the tty directory.

Fix multi-line prompt.

Remove clippy dependency

Use `cargo clippy` instead.

fix musl

Release 0.2.3

Replace use of unstable features