Don't cache Cargo registry

Author: Xanewok

.travis.yml

@@ -8,6 +8,9 @@ branches:
 cache:
   cargo: true
   timeout: 300
+# Quicker to fetch that during the build than to transmit as part of the cache
+before_cache:
+- rm -rf /home/travis/.cargo/registry
 os:
 - linux
 - osx