Include a second example

Add an example showing how to return the stream as the hint rather than a callback.   

Also demonstrate how gulp is smart about task dependency and doesn't rerun tasks that are mentioned multiple times.
return stream for styles task
fix typo and remove extra headers
fix typo in comment
fix wording and puncuation
update to use gulp-rimraf instead of gulp-clean
match require variable for rimraf
tweak some wording about completion hints
use rimraf instead of gulp-rimraf
indent .pipe()s and punctuate sentences

also spell big words correctly
Merge pull request #394 from lubelski/patch-1

Include a second example for task dependency