fix(dev-utils): Make chai a dev dependency since exported interface depends on it

packages/dev-utils/package.json

@@ -32,7 +32,6 @@
         "@0xproject/tslint-config": "^1.0.8",
         "@types/lodash": "4.14.104",
         "@types/mocha": "^2.2.42",
-        "chai": "^4.0.1",
         "make-promises-safe": "^1.1.0",
         "mocha": "^4.1.0",
         "npm-run-all": "^4.1.2",
@@ -48,6 +47,7 @@
         "@0xproject/utils": "^2.0.2",
         "@0xproject/web3-wrapper": "^3.0.3",
         "@types/web3-provider-engine": "^14.0.0",
+        "chai": "^4.0.1",
         "ethereum-types": "^1.0.11",
         "lodash": "^4.17.5"
     },