Update version numbers.

Add source for Metamask future fix.
Consolidate switch statement to one return

packages/0x.js/CHANGELOG.json

@@ -1,6 +1,6 @@
 [
     {
-        "version": "pending",
+        "version": "1.0.1-rc.4",
         "changes": [
             {
                 "pr": 914,

packages/0x.js/src/0x.ts

@@ -237,7 +237,7 @@ export class ZeroEx {
      * @param   orderHash       Hex encoded orderHash to sign.
      * @param   signerAddress   The hex encoded Ethereum address you wish to sign it with. This address
      *          must be available via the Provider supplied to 0x.js.
-     * @param   signerType the type signer that will perform the `eth_sign` operation. E.g Default, Metamask, Ledger or Trezor.
+     * @param   signerType the signer type that will perform the `eth_sign` operation. E.g Default, Metamask, Ledger or Trezor.
      *          Some implementations exhibit different behaviour. Default will assume a spec compliant eth_sign implementation.
      *          This parameter is defaulted to `SignerType.Default`.
      * @return  A hex encoded string of the Elliptic curve signature parameters generated by signing the orderHash and signature type.