readme - illustrate how to pass in options

I've gotten multiple questions on this, so it's not clear.
Update README.md dependency badge

Brings the dependency badge in line with the rest of the badges.
Merge pull request #126 from yoshuawuyts/patch-1

Update README.md dependency badge
Merge pull request #125 from sindresorhus/patch-1

readme - illustrate how to pass in options
Merge pull request #124 from stryju/master

added recipe: "Using external config file"
added custom gulpfile path/name and base options