message: Refactor: software wallet `Class` covariance
  This gives us the ability to remove all the flow fix declarations
diff: @@ -124,11 +124,7 @@ class SoftwareWallet extends EtherWallet {
  * to memoize the getter, so we're doing that here as well.
  */
  Object.defineProperty(
  - this,
  - /*
  - * Flow doesn't like getter-only props
  - */
  - /* $FlowFixMe */
  + (this: any),
  'addressQR',
  Object.assign({}, GETTER_PROP_DESCRIPTORS, {
  value: qrcode.toDataURL(this.address, QR_CODE_OPTS),
  @@ -156,11 +152,7 @@ class SoftwareWallet extends EtherWallet {
  * to memoize the getter, so we're doing that here as well.
  */
  Object.defineProperty(
  - this,
  - /*
  - * Flow doesn't like getter-only props
  - */
  - /* $FlowFixMe */
  + (this: any),
  'blockie',
  Object.assign({}, GETTER_PROP_DESCRIPTORS, { value: blockiePromise }),
  );
  @@ -181,11 +173,7 @@ class SoftwareWallet extends EtherWallet {
  * to memoize the getter, so we're doing that here as well.
  */
  Object.defineProperty(
  - this,
  - /*
  - * Flow doesn't like getter-only props
  - */
  - /* $FlowFixMe */
  + (this: any),
  'privateKeyQR',
  Object.assign({}, GETTER_PROP_DESCRIPTORS, {
  value: qrcode.toDataURL(this.privateKey, QR_CODE_OPTS),
  @@ -329,17 +317,8 @@ class SoftwareWallet extends EtherWallet {
  /*
  * We need to use `defineProperties` to make props enumerable.
  * When adding them via a `Class` getter/setter it will prevent that by default
  - *
  - * We're dealing with `defineProperty` so we need to quiet down Flow.
  - * This is because Flow, and how it doesn't play well (at all, really...)
  - * with getters and setters. See the bellow issue for more info.
  - *
  - * @FIXME Remove `Flow` error suppression when it gets fixed
  - * See: https://github.com/facebook/flow/issues/285
  - *
  - * $FlowFixMe
  */
  -Object.defineProperties(SoftwareWallet.prototype, {
  +Object.defineProperties((SoftwareWallet: any).prototype, {
  keystore: GETTER_PROP_DESCRIPTORS,
  addressQR: GETTER_PROP_DESCRIPTORS,
  blockie: GETTER_PROP_DESCRIPTORS,
  