Update README.md to include example build task

Resolves #251. Hoping this helps others understand that usemin won't run the concat/cssmin/uglify tasks for you.
Merge pull request #350 from XhmikosR/master

Use lodash more.
Fix <img src> not being replaced when followed by ng-src
Merge pull request #342 from tedjp/ng-src

Fix <img src> not being replaced when followed by ng-src
Merge pull request #311 from zfarrell/readme-add-task-example

Update README.md to include example build task
Update README.md.
Fix typos in comments.