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 #517 from phated/master

return early on error, stop using isNull() when it is an empty block - better than #513
update docs to reflect new changes
Update using-multiple-sources-in-one-task.md
3.8.0
Merge branch 'master' of https://github.com/gulpjs/gulp
Fixed typo
Merge pull request #520 from appleboy/patch-1

Fixed typo
Merge pull request #394 from lubelski/patch-1

Include a second example for task dependency
README.md: Change order of 'default' task dep

With proper error handling, this keeps `gulp.watch` running, even when the build steps fail.

See also https://github.com/felixrabe/gulp-setup for my own setup.
Merge pull request #528 from felixrabe/patch-1

README.md: Change order of 'default' task dep