Add assets/javascript/vendor to default test project dir structure
Fail test project build on errors
Retry npm install in test project

npm install randomly fails (using npm v1.4.26), retrying a few
times to make tests more robust
Remove trailing whitespace
Remove mimosa-jscs from npm cache before running tests
Change behaviour of vendor option

Setting vendor to true lints copied vendor file regardless
of copy option. Compiled vendor files are never linted.

This is to have the same behavior as jshint, jshint.vendor
documentation:

jshint.vendor
When this property is set to true, Mimosa will execute jshint
on the successful copy of a vendor JavaScript asset.
Add tests for coped, compiled, vendor options