Do not require 'children' as missing prop

[seekshiva]

When the prop-types rules is on, don't ask 'children' to be declared in propType. It is provided by React by default.

[yannickcr]

It as already been discussed in #7, see "As for exceptions" section in documentation.

If you do not want to declare a propType for props.children you can still add it to the ignore list (see rules options)

[seekshiva]

Thanks