Removed a dependency, switched to babel proposal

For ESDoc, switch to babel proposal syntax, the es7 plugin was causing a
problem that I couldn't fix myself.

esdoc.json

@@ -2,7 +2,9 @@
   "source": "./src",
   "destination": "./docs",
   "excludes": ["node_modules"],
-  "plugins": [{
-    "name": "esdoc-es7-plugin"
-  }]
+  "experimentalProposal": {
+    "classProperties": true,
+    "objectRestSpread": true
+  },
+  "plugins": []
 }

package.json

@@ -52,8 +52,7 @@
     "babel-preset-stage-0": "^6.1.18",
     "chai": "^3.4.1",
     "chai-as-promised": "^6.0.0",
-    "esdoc": "^0.5.1",
-    "esdoc-es7-plugin": "0.0.3",
+    "esdoc": "^0.5.2",
     "esdoc-node": "^1.0.1",
     "eslint": "^3.12.1",
     "eslint-config-airbnb": "^13.0.0",