Add missing translation
Return false, not '', if there is no search term
Standardize class documentation and magic methods
Commit missed removal
Standardize set_ and reset_properties() methods
Add and standardize getters; clarify method name
Bail on saving non-array post types and taxonomies
Bail on saving unexpectedly non-string fields
Refuse to format() non-strings
Add initial unit tests
Clarify and de-dupe some docs
Fix inconsistent capitalization
Tweak .travis.yml
Remove the reset_properties() methods

These methods were added only for unit tests, but cleaning up the
properties and the surrounding environment is more easily handled in the
tests responsible for the changes.

Also fixes a bug in resetting WP_SEO::formatting_tags where missing tags
wouldn't be removed from the array once added.
Add set_options() method and update get_option()
Move nonce verification into separate conditionals

Allows us to see more specifically why verification failed, particularly
in testing.
Mark some methods as @codeCoverageIgnore
Spit and polish
Update phpunit.xml for code coverage reports
Clean up setUp() and tearDown() in formatting-tags tests