Added some more documentation to README.md
Smaller headings, ocd
Added 'ini' and 'json' configuration file examples to show support for comments and nested objects.
Added note about options being merged instead of replaced, and clarification about file extensions not mattering for ini vs. json config files.
Fixed the JSON example (remove trailing comma)
Added caveat about ini sections being supported only one level deep
Added warning about passed-in defaults being mutated and a note on performance.
Fixed typos.
explained that the third argument is for custom opts parser
cleared up my previous confusion about nested objects in .ini config files
Update README.md
Merge pull request #20 from mikermcneil/master

Additions to README