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.

* Add travis integration

* Update examples/rainbow to work on stable

No.

We use click and drag.

* modify Keys and Events to detect Esc key presses

The strategy used here is to read two bytes at a time, going on the
assumption that escape sequences will consist of multi byte reads and
solitary Esc key presses will consist of single byte reads.

Tests had to be modified to account for these new multi byte reads by
including dummy bytes when a single byte was previously expected.

Fixes ticki/termion#43

* expand keys example to include Esc key presses

* add test for Esc key press

Commit 0d1025c5 changed the signature of
is_tty, but the example was not updated.

This adds support for the escape codes generated in rxvt and xterm
format by holding a button and moving the mouse around.

fix message not appearing

This commit is a major semver bump. Every progra utilizing escape codes generated by Termion is likely broken. The main change is to make each escape has their own type implementing the Display trait.

- Use formatters, mainly Display for escapes.

- Add Truecolor support (`color::Rgb`).

- Put each primitive into distinct modules.

- Add is_tty for checking if some stream is a TTY.

- Add multiple new examples.

The event system has been reworked to allow the detection of mouse
events as well as key presses.
Xterm, rxvt and X10 emulated escape codes are supported, they are
enabled and disabled by sending the right escape codes when creating a
RawTerminal.

To allow for byte manipulation, which was necessary to implement those
features, the backend iterator has been changed from chars() to bytes()
(with specific treatment of unicode sequences), making the whole crate
not require nightly rustc.

Mode is somewhat ambiguous term, which is often overused, for that reason I want to avoid it. This is a breaking change, but I don't guarantee stability yet, however I'll do my best to not break things.