Device names must be 50 chars or less

Fixes #762

// FREEBIE

options.html

@@ -49,7 +49,7 @@
           <img id='signal-computer' src='/images/signal-laptop.png'>
           <p>{{ installComputerName }}</p>
           <div>
-            <input type='text' id='device-name' spellcheck='false'></input>
+            <input type='text' id='device-name' spellcheck='false' maxlength='50' />
           </div>
           <div class='nav'>
             <div> <a class='button' id='sync'>{{ installFinalButton }}</a> </div>