Expand Travis test matrix

.travis.yml

@@ -1,8 +1,10 @@
-language: python
+language: python                # Lua!
 sudo: false
 
 env:
   - LUA="lua=5.1"
+  - LUA="lua=5.2"
+  - LUA="lua=5.3"
   - LUA="luajit=2.0"
   - LUA="luajit=2.1"
 
@@ -18,7 +20,7 @@ install:
   - luarocks install luacov-coveralls
 
 script:
-  - luacheck --std lua51+luajit src
+  - luacheck --std max src
   - luacheck --std busted spec
   - busted --verbose --coverage