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
Change all the emphasis "headings" to headings

By using headings for each section under the intro instead of emphasis
tags, GitHub exposes anchors that make each section linkable.
Unfortunately headings need to be on one line.
Merge pull request #28 from amaltson/readme-anchors

Change all the emphasis "headings" to headings
Pass options to #defer
Move definition of conversion functions out of module initializer.