Additions to README

[mikermcneil]

Just some minor stuff I ran into:

• Added explanation of how to use the third argument to rc (presumably for unit testing)
• Added a clarification that the result of calling require('rc', 'foo', {}) will be your config. Sort of obvious, but I still had to check the first time I used the library. Maybe I'm just dense :)

[mikermcneil]

The last few commits are just me adding some more examples and explaining the details about how parts of it work (especially the merging together of objects, which is intuitive, but helpful to know right out the gate so you don't have to check to see if it works). Also mentioned the support for ini sections for nested objects.

[mikermcneil]

And the last bit is just a note to make sure folks (err like me) understand you can't do things like:

[foo]
  works=true
  [bar]
    works=false

(results in foo: { works: false, '[bar]': true, stuff: 'ok' })

Which is fine, because the ini format doesn't allow for nested sections, but still worth pointing out I think.

[mikermcneil]

ok now I'm done- added:

• warning that a passed-in defaults object will be mutated
• caveat about performance at the end (uses synchronous fs stuff so don't put it somewhere silly)

[mikermcneil]

fixed some typos, good to go now

[dominictarr]

Awesome pull request!

Just 2 things: you can have nested objects in ini, but it works different:
instead basically, you have dotted paths, instead of nested sections.

{
 "foo": {"bar": {"baz": "value"}}
}

can be represented in ini as:

[foo.bar]
baz = value

see: https://github.com/isaacs/ini#usage

this is also described in the wikipedia page http://en.wikipedia.org/wiki/INI_file#Hierarchy

The third argument is incase you really want to use a different opts parser: #12

can you fix these two points and I'll merge!

[mikermcneil]

Good to know, thanks!

[mikermcneil]

okie dokie, that should clear it up. Apologies on the delay!

[dominictarr]

cool, merging!

[dominictarr]

merged into 0.3.3