Rename global variable 'Chat' to 'Snapdrop'

Initially a lot of code was copied from another project. This lead to confusing naming conventions.

app/elements/text-sharing/clipboard-behavior.html

@@ -8,7 +8,7 @@
     style.top = '-10000px';
     document.body.appendChild(copyTextarea);
 
-    window.Chat.ClipboardBehavior = {
+    window.Snapdrop.ClipboardBehavior = {
         copyToClipboard: function(content) {
             copyTextarea.value = content;
             var range = document.createRange();

app/elements/text-sharing/text-input-behavior.html

@@ -1,12 +1,12 @@
 <link rel="import" href="text-input-dialog.html">
 <script>
 'use strict';
-window.Chat = window.Chat || {};
+window.Snapdrop = window.Snapdrop || {};
 (function() {
     var textInput = Polymer.Base.create('text-input-dialog');
     textInput.className = 'textInput';
     document.body.appendChild(textInput);
-    Chat.TextInputBehavior = {
+    Snapdrop.TextInputBehavior = {
         properties: {
             contact: Object,
         },

app/elements/text-sharing/text-input-dialog.html

@@ -91,7 +91,7 @@
 
         Polymer({
             is: 'text-input-dialog',
-            behaviors: [Chat.ClipboardBehavior, Chat.SoundNotificationBehavior],
+            behaviors: [Snapdrop.ClipboardBehavior, Snapdrop.SoundNotificationBehavior],
             properties: {
                 textToSend: {
                     type: String