Move isAddress to shared utils and remove all dependencies on ethereum-address

packages/website/ts/components/inputs/address_input.tsx

@@ -1,4 +1,4 @@
-import {isAddress} from 'ethereum-address';
+import {addressUtils} from '@0xproject/utils';
 import * as _ from 'lodash';
 import {colors} from 'material-ui/styles';
 import TextField from 'material-ui/TextField';

packages/website/ts/globals.d.ts

@@ -55,11 +55,6 @@ interface System {
 }
 declare var System: System;
 
-// ethereum-address declarations
-declare module 'ethereum-address' {
-    export const isAddress: (address: string) => boolean;
-}
-
 // jsonschema declarations
 // Source: https://github.com/tdegrunt/jsonschema/blob/master/lib/index.d.ts
 declare interface Schema {