docs(tagsInput): Fix small issues

Fix small issues so the docs are ngdoc-compliant.
chore(Gruntfile): Add ng-doc task
feat(tagsInput): Add support for array of objects

Drop support for array of strings and add support for array of objects as
a list of tags. Introduce a new option, display-property, so the user can
set what property should be used as the tag text. The option defaults to
"text".

BREAKING CHANGE: From now on, array of strings are no longer supported. In
order to keep some backward compatibility a one-time conversion from an
array of strings into an array of objects is available.

Closes #46.
chore(git): Merge branch 'master' of https://github.com/mbenford/ngTagsInput

Merge changes in README done from GitHub web interface.
refactor(tagsInput): Remove redundant code

Remove redundant code (function calls, scope usage etc) from both
tagsInput and autoComplete directives.