Run build on travis.

.travis.yml

@@ -7,4 +7,5 @@ install:
   - npm install
 
 script:
+  - npm run build
   - npm run test

tools/run_python.js

@@ -1,8 +0,0 @@
-let cp = require ('child_process');
-let pythonExecutable = 'python';
-if (process.platform !== 'win32') {
-    pythonExecutable = 'python3';
-}
-cp.spawnSync (pythonExecutable, process.argv.slice (2), {
-    stdio: "inherit"
-});