Added a note to reverse-word.js about the need for Handlebars helpers to contain a dash.

Handlebars helpers' name need to have a dash, or they won't be found by the (lazy) resolver, unless they're declared explicitly. I added a note to the reverse-word.js example to help make this clear.
Shortened the note added to reverse-word.js about the need for a dasherized name.
Replaced the URL to get more details in the reverse-word.js file.
Merge pull request #326 from claudeprecourt/patch-1

Added a note to reverse-word.js about the need for Handlebars helpers to contain a dash.