Minimize binary size.

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,3 +20,9 @@ directories = "2.0.1"
 regex       = "1.1.7"
 num         = "0.2"
 term_size   = "0.3"
+
+[profile.release]
+codegen-units = 1
+lto = true
+opt-level = "z"
+panic = "abort"