docs(guide/templates): clarity
docs(guide/services): rewrite services documentation
docs(guide/bootstrap): fix formatting
docs(guide/css-styling): rename and fix formatting
docs(guide/e2e-testing): rename and fix formatting
docs(guide/unit-testing): rename and fix formatting
docs(guide/introduction): reword for clarity
docs(guide/concepts): fix links
docs(guide/controller): reorganize, add Controller suffix, formatting
docs(guide/databinding): reword for clarity
docs(guide/di): fix formatting and improve clarity
docs(guide/module): improve clarity
chore(grunt): remove unnecessary white spaces
docs(tutorial/index): improve accessibility

- Adds accessibility attributes to links and images.
- Adds a note on using NVM for node.
docs(tutorial): update step_08.ngdoc

Closes #6537
docs(guide/forms): fix a typo

Closes #6556
docs(guide/services): clean up typos
docs(tutorial): update step_09.ngdoc

Closes #5991
docs(directive.ngdoc): typo fix
style: enable jscs requireLeftStickedOperators rule

Closed #6544.