Update doc:json command to exclude privates and externals

package.json

@@ -21,7 +21,7 @@
     "test:coverage": "nyc npm run test --all",
     "update_contracts": "for i in ${npm_package_config_artifacts}; do copyfiles -u 4 ../contracts/build/contracts/$i.json ../0x.js/src/artifacts; done;",
     "testrpc": "testrpc -p 8545 --networkId 50 -m \"${npm_package_config_mnemonic}\"",
-    "docs:json": "typedoc --json docs/index.json .",
+    "docs:json": "typedoc --excludePrivate --excludeExternals --target ES5 --json docs/index.json .",
     "docs:generate": "typedoc --out docs .",
     "docs:open": "opn docs/index.html",
     "clean": "shx rm -rf _bundles lib test_temp",