Improve documentation on how to use the script.
Catch exceptions in before-save-hook for safety.
Fix private function naming convention.

It seems that if a private function is named `js2-closure--foo` then
it'll show up in the `M-x` tab completion window. However if the name is
`js2--closure-foo`, then everything appears fine.
Regenerate README.md (forgot to run in d805b0a6c407e602b802abab6b641f8551adcab9)
Update version to 1.2 in source code.
Don't require nested namespaces.

gjslint will complain if we include namespaces like `foo.Bar.Lol` since
it only wants us to require `foo.Bar`. There are numerous examples of
such namespaces being provided in the Closure Library code, like
`goog.format.JsonPrettyPrinter.TextDelimiters`.