docs(tutorial/step-4): fix e2e test

After a protractor update the test syntax had to be changed.

Closes #7919
docs(ngMessages): correct a typo

Closes #7918
fix(Angular): nodeName should always be lowercase

XHTML uses lowercase node names, while HTML often uses uppercase.  The
generally accepted convention is to always lowercase them.

Fixes #3987
docs($provide): it is a service not an object

Closes #7917
fix(input): escape forward slash in email regexp

This messed up with syntax coloring and variable hovering in chrome developer tools and made debugging really difficult.

Closes #7938
Make angular.equals support objects with circular references