Update rust version to 1.32.0 and run clippy

.gitlab-ci.yml

Makefile

README.md

benches/statement.rs

members/braces/src/lib.rs

src/binary/completer.rs

src/binary/mod.rs

src/binary/prompt.rs

src/binary/readln.rs

src/lib/builtins/command_info.rs

src/lib/builtins/exec.rs

src/lib/builtins/exists.rs

src/lib/builtins/functions.rs

src/lib/builtins/is.rs

src/lib/builtins/job_control.rs

src/lib/builtins/mod.rs

src/lib/builtins/set.rs

src/lib/builtins/source.rs

src/lib/builtins/status.rs

src/lib/builtins/variables.rs