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.

Codes of the form `ESC [ < 3 ; Cx ; Cy` were not supported before.

At least on FreeBSD and OpenBSD, TIOCGWINSZ == 0x40087468 just like on
macOS, so change the definition from not-macOS/macOS to Linux/non-Linux.

This solves #85 in a similar fashion as the color amount detection: the
cursor module now provides a trait that adds a `cursor_pos()` method to
an instance of `Write`. It also corrects that previous implementation
somewhat by making the `CONTROL_SEQUENCE_TIMEOUT` a member of the raw
module and implementing `DetectColors` for any instance of `Write`
rather than just `RawTerminal` (`MouseTerminal` for instance works as
well).

* Add (optional) support for alternate screen (#77)

The user can manually switch between main and alternate screen or
(preferably) use the wrapper struct for automatic screen restoration.

* Add two examples for screen switching

* Improve screen module documentation

* Added color support detection

Color support is inferred by using either OSC 4 escape codes or the
value of TERM.

* minor refactor and cosmetic changes

`std::io::Write` doesn't guarantees that it will write everything,
and could even return a non-fatal `ErrorKind::Interrupted` error.
`write_all` has exactly the code required to deal with this.

thx svgo