remove windows specific cmd running casper

missing ```test``` parameter executing casperjs results in the following error:
```
casperjs .\demo\testsuite.js
ReferenceError: Can't find variable: casper

  C:/DEV/WEB/visual_regression-test/EVAL/PhantomCSS/phantomcss.js:47 in update
  C:/DEV/WEB/visual_regression-test/EVAL/PhantomCSS/phantomcss.js:73 in init
  .\demo\testsuite.js:7
Hint: you may want to use the `casperjs test` command.
```

according to the [documentation](http://docs.casperjs.org/en/latest/testing.html#index-0) the subcommand ```test``` is needed in conjunction with the testing framework