Try fixing OSX builds

... that I broke by introducing travis-cargo.

.travis.yml

@@ -21,12 +21,12 @@ addons:
 before_script:
 - |
   pip install 'travis-cargo<0.2' --user &&
-  export PATH=$HOME/.local/bin:$PATH
+  export PATH=$HOME/.local/bin:/usr/local/bin:$PATH
 
 script:
 - |
-  travis-cargo build &&
-  travis-cargo test
+  cargo build &&
+  cargo test
 
 after_success:
 - travis-cargo coveralls --no-sudo