modify Keys and Events to detect Esc key presses

Created by: iamcodemaker

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