Achieve 100% doc coverage [DONE]

see: https://github.com/rspec/rspec-core/issues/1334

currently:
```
Files:          48
Modules:        31 (   21 undocumented)
Classes:        50 (   27 undocumented)
Constants:      27 (   25 undocumented)
Methods:       388 (  202 undocumented)
 44.56% documented
```

DONE:
```
yard stats --list-undoc
Files:          30
Modules:        17 (    0 undocumented)
Classes:        25 (    0 undocumented)
Constants:       3 (    0 undocumented)
Methods:       142 (    0 undocumented)
 100.00% documented

```