Fix TIOCGWINSZ type mismatch on DragonFly

See merge request redox-os/termion!152

Below is the error message I got before this patch:

    error[E0308]: mismatched types
      --> src/sys/unix/size.rs:17:34
       |
    17 |         cvt(ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut size as *mut _))?;
       |                                  ^^^^^^^^^^ expected u64, found u32
    help: you can cast an `u32` to `u64`, which will zero-extend the source value
       |
    17 |         cvt(ioctl(STDOUT_FILENO, TIOCGWINSZ.into(), &mut size as *mut _))?;
       |                                  ^^^^^^^^^^^^^^^^^

Add ability to suspend/activate raw mode on RawTerminal

See merge request redox-os/termion!150

Reconfigure CI

See merge request redox-os/termion!148

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