Upgrade rust/crates/regex to 1.5.4

Test: make
Change-Id: I0eab39246dc2aea41a62c15661e350b490f06c1d
diff --git a/tests/test_default.rs b/tests/test_default.rs
index af634a0..d4365fb 100644
--- a/tests/test_default.rs
+++ b/tests/test_default.rs
@@ -1,7 +1,6 @@
 #![cfg_attr(feature = "pattern", feature(pattern))]
 
-extern crate rand;
-extern crate regex;
+use regex;
 
 // Due to macro scoping rules, this definition only applies for the modules
 // defined below. Effectively, it allows us to use the same tests for both