Enable cache for cargo packages.

jschlumpp · jschlumpp · commit f6b6de92b5bc · 2017-07-18T09:55:49.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,7 @@
 sudo: required
 dist: trusty
 language: rust
+cache: cargo
 rust:
   - nightly
 
