PLT-2816 Fixed handling of Unicode 8 emojis (#2924)

* Updated twemoji to properly recognize Unicode 8.0 emojis

* Updated unicode emoji parser to only render emojis we support as images

* Corrected filename for South African flag emoji

* Added Mattermost emoticons!

* Added additional emoticons to test files

webapp/components/suggestion/emoticon_provider.jsx

@@ -55,7 +55,7 @@ export default class EmoticonProvider {
 
             const matched = [];
 
-            for (const [name, emoticon] of Emoticons.emoticons) {
+            for (const [name, emoticon] of Emoticons.getEmoticonsByName()) {
                 if (name.indexOf(partialName) !== -1) {
                     matched.push(emoticon);