I may be wrong but I don't understant why it is not already the case...
And add some missing documentation.

Attempt to fix #63.
Fix AltGr key.

Iterate on keys pressed instead of chars

Only the unix implementation works.
The windows impl does not even compile...

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.