The purpose of this API is basically to satisfy AMO reviewers in the
future, since the use of innerHTML with variables (i.e., not plain text) will
be rejected without any questions.
Since this is not a problem for browsers other than Firefox, they will
use simple innerHTML assignment, however safe-parsing could be implemented
for them too.
.jshintrc's otion-set is a personal choice, merely a suggestion.
Beside that, it includes some common globals for specific browsers, so
there's no need to set the globals in every .js file.
In order to force strict coding, "use strict" directive was added into
every .js file.
