Remove transient build artifacts from Travis cache

Author: mhallin

.travis.yml

@@ -70,5 +70,11 @@ after_deploy:
 
 before_cache:
   rm -rf target/debug/juniper*
+  rm -rf target/debug/libjuniper*
+  rm -rf target/debug/.fingerprint/juniper*
+
   rm -rf target/release/juniper*
+  rm -rf target/release/libjuniper*
+  rm -rf target/release/.fingerprint/juniper*
+
   rm -rf target/package/