Update to use latest snapcraft features

Makefile

@@ -1,5 +0,0 @@
-all:
-
-install:
-	wget https://downloads.plex.tv/plex-media-server/1.2.2.2857-d34b464/plexmediaserver_1.2.2.2857-d34b464_amd64.deb -O plexmediaserver.deb
-	dpkg-deb -x plexmediaserver.deb $(DESTDIR)

snapcraft.yaml

@@ -1,4 +1,4 @@
-name: plexmediaserver
+name: plex-mediaserver
 version: 1.2.2.2857-d34b464-1
 summary: Unofficial snap for the Plex media server
 architectures: [amd64]
@@ -20,9 +20,9 @@ apps:
 parts:
   common:
     plugin: dump
-    source: .
-    snap:
-      - bin/server.sh
+    source: bin
+    organize:
+      server.sh: bin/server.sh
   plexmediaserver:
-    plugin: make
-    source: .
+    plugin: dump
+    source: https://downloads.plex.tv/plex-media-server/1.2.2.2857-d34b464/plexmediaserver_1.2.2.2857-d34b464_amd64.deb