Move cytoscape to peer dependencies for saner bundling

Refs #17
Refs #28

Author: akx

package.json

@@ -34,7 +34,8 @@
     "start": "run-s watch"
   },
   "peerDependencies": {
-    "react": ">=15.0.0"
+    "react": ">=15.0.0",
+    "cytoscape": "^3.2.19"
   },
   "devDependencies": {
     "chai": "^4.1.2",
@@ -59,7 +60,6 @@
     "node": ">=8.11.3"
   },
   "dependencies": {
-    "cytoscape": "^3.2.19",
     "prop-types": "^15.6.2"
   }
 }