Upgrade markdown packages

package.json

@@ -89,7 +89,7 @@
     "image-view": "0.33.0",
     "keybinding-resolver": "0.17.0",
     "link": "0.22.0",
-    "markdown-preview": "0.69.0",
+    "markdown-preview": "0.70.0",
     "metrics": "0.32.0",
     "open-on-github": "0.28.0",
     "package-generator": "0.30.0",
@@ -110,7 +110,7 @@
     "language-c": "0.15.0",
     "language-coffee-script": "0.22.0",
     "language-css": "0.16.0",
-    "language-gfm": "0.34.0",
+    "language-gfm": "0.35.0",
     "language-git": "0.9.0",
     "language-go": "0.11.0",
     "language-html": "0.19.0",