Use 'config' terminology to refer to the builder object.
Add BlankSlate to the prior art list.
Fix minor formatting issue in the README.
Enable special customization for predicate methods.
Get coverage up to 100%
Merge pull request #21 from dandorman/readme-formatting-fix

Fix minor formatting issue in the README.
Use `module_exec` instead of `module_eval` whenever having variables
Merge pull request #24 from samnang/use_module_exec

Use `module_exec` instead of `module_eval` whenever having variables
Update other instances of module_eval to module_exec if it needed parameters
Merge pull request #25 from samnang/use_module_exec

Update other instances of module_eval to module_exec if it needed parameters
Split NullClassBuilder#define_basic_methods into two smaller (private) methods
Extract operation application into #apply_operations method
Merge pull request #26 from gcapizzi/small_refactorings

Some small refactorings