Extra derives & performance optimizations

See merge request redox-os/termion!149

The import of std::ascii::AsciiExt in src/event.rs is unused. Remove it.

> warning: unused import: `std::ascii::AsciiExt`
>  --> src/event.rs:4:5
>   |
> 4 | use std::ascii::AsciiExt;
>   |     ^^^^^^^^^^^^^^^^^^^^
>   |
>   = note: #[warn(unused_imports)] on by default

This change removes an unused 'mut' qualifier of the 'source' variable
in src/input.rs.

> warning: variable does not need to be mutable
>   --> src/input.rs:52:13
>    |
> 52 |         let mut source = &mut self.source;
>    |             ----^^^^^^
>    |             |
>    |             help: remove this `mut`
>    |
>    = note: #[warn(unused_mut)] on by default

Fix detect cursor position reading extra byte

Update references to repository

use `TIOCGWINSZ` directly from `libc`

Move system specific features into sys module

Update tty.rs

Implement size and is_tty with termios on Redox

Add an Iterator on Read that provides both the parsed event and the byte sequence that defines it

- In addition to Events it preserves the byte sequence that created an event. This
  is useful, e.g., for implementing a terminal multiplexer where the raw input
  should in some cases be passed on to another tty.
- In order to ensure backwards compatibility, the function that creates the trait
  is implemented in a separate extension trait.

Fix raw mode on Redox

run travis builds on osx also

fix #99

Add support for F1-F5 in the linux tty.

added cursor position detection

parse_utf8_char() makes the assumption that at least four bytes or one UTF-8 glyph are still to read in the input.