Add optional delim argument

This is useful for parsing/stringifying cookie values.
fix #11: flattened keys in array are now correctly parsed
Merge pull request #13 from maxleiko/master

fix #11: flattened keys in array are now correctly parsed
cleanup for #13
Merge pull request #12 from mjackson/opt-delim

Add optional delim argument
Merge branch 'master' of github.com:hapijs/qs
cleanup for #12
update readme
fix formatting
cleanup comparisons to undefined
1.2.0
Close code block
Merge pull request #15 from hatchan/patch-1

Close code block
ignore non-string delimiters
Merge pull request #16 from bengl/nonstringdelim

ignore non-string delimiters
1.2.1
Create CONTRIBUTING.md
Don't overwrite null values
Adding a test
Merge pull request #19 from wpreul/master

Don't overwrite null values