Upgrade xterm to 3.1

package.json

@@ -32,7 +32,7 @@
     "rxjs": "^5.5.2",
     "rxjs-websockets": "^4.0.0",
     "showdown": "^1.8.5",
-    "xterm": "^3.0.1",
+    "xterm": "^3.1.0",
     "zone.js": "^0.8.14"
   },
   "devDependencies": {

yarn.lock

@@ -6755,9 +6755,9 @@ xtend@^4.0.0, xtend@^4.0.1, xtend@~4.0.1:
   version "4.0.1"
   resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.1.tgz#a5c6d532be656e23db820efb943a1f04998d63af"
 
-xterm@^3.0.1:
-  version "3.0.2"
-  resolved "https://registry.yarnpkg.com/xterm/-/xterm-3.0.2.tgz#1acc6317367f4290b6be2d4ac1af0d2631fdbb35"
+xterm@^3.1.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/xterm/-/xterm-3.1.0.tgz#7f7e1c8cf4b80bd881a4e8891213b851423e90c9"
 
 xxhashjs@^0.2.1:
   version "0.2.2"