Try radically changing the Travis script

.travis.yml

@@ -1,24 +1,14 @@
-matrix:
+language: python
-  include:
-    - language: rust
-      rust:
-      - stable
-      - beta
-      - nightly
-      matrix:
-        allow_failures:
-          - rust: nightly
-      cache: cargo
 
-    # http://kiki.to/blog/2016/02/04/talk-continuous-integration-with-lua/
-    - language: python
 env:
-        - LUA="lua=5.1"
+  - RUST="stable" LUA="lua=5.1"
+  - RUST="beta" LUA="lua=5.1"
 
 before_install:
   - pip install hererocks
   - hererocks lua_install -r^ --$LUA
   - export PATH=$PATH:$PWD/lua_install/bin
+  - curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain $RUST
 
 install:
   - luarocks install luafilesystem
@@ -30,6 +20,7 @@ matrix:
 script:
   - cd plugin && luacheck . && cd ..
   - lua -lluacov spec.lua
+  - cargo test --verbose
 
 after_success:
   - luacov-coveralls -e $TRAVIS_BUILD_DIR/lua_install