Fixed several english issues.

i18n/en.i18n.json

@@ -423,7 +423,7 @@
   "Settings" : "Settings",
   "Settings_updated" : "Settings updated",
   "Should_be_a_URL_of_an_image" : "Should be a URL of an image.",
-  "Should_exists_a_user_with_this_username" : "Should exists a user with this username.",
+  "Should_exists_a_user_with_this_username" : "The user must already exist.",
   "Showing_online_users" : "Showing <b>__total_online__</b> of __total__ users",
   "Showing_results" : "<p>Showing <b>%s</b> results</p>",
   "Silence" : "Silence",
@@ -535,8 +535,8 @@
   "Yes_clear_all" : "Yes, clear all!",
   "Yes_delete_it" : "Yes, delete it!",
   "you_are_in_preview_mode_of" : "You are in preview mode of channel #<strong>__room_name__</strong>",
-  "You_can_change_a_different_avatar_too" : "You can change a different avatar too",
-  "You_can_use_an_emoji_as_avatar" : "You can use an emoji as avatar",
+  "You_can_change_a_different_avatar_too" : "You can override the avatar used to post from this integration.",
+  "You_can_use_an_emoji_as_avatar" : "You can also use an emoji as an avatar.",
   "You_have_been_muted" : "You have been muted and cannot speak in this room",
   "You_need_confirm_email" : "You need to confirm your email to login!",
   "You_need_install_an_extension_to_allow_screen_sharing" : "You need install an extension to allow screen sharing",