Allow to named resources

By using `resource=""`. `resource=true` can still be used.

In reference with this PR #256.

### Before

![before](https://github-camo.global.ssl.fastly.net/2c40bfca981635c24846de507b14b5f21093d857/687474703a2f2f696d616765736861636b2e75732f612f696d673832322f353230322f687339392e706e67)

### After
![after](https://github-camo.global.ssl.fastly.net/2259af41c03a213d4b958947065415ce90317b0a/687474703a2f2f696d616765736861636b2e75732f612f696d673534322f363038322f696f70382e706e67)