Move from using lerna multi-package commands to wsrun, update README's accordingly

packages/base-contract/README.md

@@ -44,14 +44,16 @@ yarn install
 
 ### Build
 
+To build this package and all other monorepo packages that it depends on, run the following from the monorepo root directory:
+
 ```bash
-yarn build
+PKG=@0xproject/base-contract yarn build
 ```
 
-or
+Or continuously rebuild on change:
 
 ```bash
-yarn build:watch
+PKG=@0xproject/base-contract yarn watch
 ```
 
 ### Lint

packages/base-contract/package.json

@@ -5,7 +5,7 @@
     "main": "lib/src/index.js",
     "types": "lib/src/index.d.ts",
     "scripts": {
-        "build:watch": "tsc -w",
+        "watch": "tsc -w",
         "build": "tsc && copyfiles -u 2 './lib/monorepo_scripts/**/*' ./scripts",
         "clean": "shx rm -rf lib scripts",
         "test": "run-s clean build run_mocha",