pin doc related deps and regen yarn lock

contracts/erc721/package.json

@@ -58,7 +58,7 @@
         "@0x/contracts-utils": "^4.5.1",
         "@0x/dev-utils": "^3.3.3",
         "@0x/sol-compiler": "^4.2.2",
-        "@0x/ts-doc-gen": "^0.0.26",
+        "@0x/ts-doc-gen": "^0.0.28",
         "@0x/tslint-config": "^4.1.3",
         "@0x/types": "^3.2.3",
         "@0x/typescript-typings": "^5.1.4",
@@ -80,7 +80,7 @@
         "solhint": "^1.4.1",
         "truffle": "^5.0.32",
         "tslint": "5.11.0",
-        "typedoc": "^0.15.0",
+        "typedoc": "~0.16.11",
         "typescript": "3.0.1"
     },
     "dependencies": {