Reset the terminal when Ctrl-C is pressed

If a user hits Ctrl-C to exit out of a search in the middle of printing
a line, we don't want to leave the terminal colors screwed up for them.
Catch Ctrl-C using the ctrlc crate, obtain a stdout lock to ensure that
other threads don't continue writing after we do so, reset the terminal,
and exit the program.

Closes #119

Cargo.toml

@@ -24,6 +24,7 @@ name = "integration"
 path = "tests/tests.rs"
 
 [dependencies]
+ctrlc = "2.0"
 deque = "0.3"
 docopt = "0.6"
 env_logger = "0.3"