Use lighter-weight simple-concat instead of concat-stream

These modules do the same thing.

$ browserify -r simple-concat --no-builtins | wc -c
901

$ browserify -r concat-stream --no-builtins | wc -c
91998

package.json

@@ -18,7 +18,6 @@
     "application-config": "^0.2.1",
     "bitfield": "^1.0.2",
     "chromecasts": "^1.8.0",
-    "concat-stream": "^1.5.1",
     "create-torrent": "^3.24.5",
     "deep-equal": "^1.0.1",
     "dlnacasts": "^0.1.0",
@@ -34,6 +33,7 @@
     "network-address": "^1.1.0",
     "prettier-bytes": "^1.0.1",
     "run-parallel": "^1.1.6",
+    "simple-concat": "^1.0.0",
     "simple-get": "^2.0.0",
     "srt-to-vtt": "^1.1.1",
     "virtual-dom": "^2.1.1",