Merge branch 'v2-prototype' into refactor/check-revert-reasons

* v2-prototype: (21 commits)
  Don't use variables for revert reasons
  Add comments to dispatchTransferFrom
  Document IAssetData
  Compute bytes4 proxyid constants
  Return inplace bytes in LibBytes.readBytesWithLength
  Add Greg's documentation to MixinErc721Transfer
  Add Greg's documentation to MixinErc20Transfer
  Gas golf the transfer success logic
  Optimize like in PR #767
  Run prettier and fix linting errors
  Fix tests
  Update tests
  Fix AssetProxyUtils
  Update tests
  Fix ERC721Proxy TokenId
  Update AssetProxyUtils
  Add IAssetData
  WIP
  ABI encoded asset data
  Remove proxyId argument from dispatchTransferFrom
  ...

# Conflicts:
#	packages/contracts/test/asset_proxy/proxies.ts

packages/types/src/index.ts

@@ -152,18 +152,18 @@ export interface ECSignature {
 }
 
 export enum AssetProxyId {
-    INVALID,
-    ERC20,
-    ERC721,
+    INVALID = '0x00000000',
+    ERC20 = '0xf47261b0',
+    ERC721 = '0x08e937fa',
 }
 
 export interface ERC20AssetData {
-    assetProxyId: AssetProxyId;
+    assetProxyId: string;
     tokenAddress: string;
 }
 
 export interface ERC721AssetData {
-    assetProxyId: AssetProxyId;
+    assetProxyId: string;
     tokenAddress: string;
     tokenId: BigNumber;
     receiverData: string;