* 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

Shamelessly copying Serde's style

* Add travis integration

* Update examples/rainbow to work on stable

Fix #53

* Discard leftover input when consumed

The iterator given to `parse_event` now `take()` the value from
`leftover`.

* Always save leftover

`parse_event` will consume it when required.

* Remove OptionIterator, directly uses std::option::Iter

* Add `UnknownCSI` event type.

* Compile test from `raw` module

But don't run it.

* Fix unused import warning in doc-test

* Rename UnknownCSI -> UnknownCsi

Bionic needs signed ioctrl arguments.

* Handles CSI `~` sequences with multiple values

Fixes #62

* Fix doc typo

Properly detects CSI sequence termination.

Fixes #47, #68.

No.

Using the "alternate screen" capability, the RawTerminal trait restores
the terminal in its previous state by sending the proper escape codes.

Move the check to the beginning of the loop to protect against empty buffer.

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