fix(REP token): renames REP to REPv1 (#915)

https://www.augur.net/blog/v2-launch/

TL;DR: Augur v2 launch is coming up and will introduce a new REP token.  FF has requested all exchanges rename REP to REPv1 to avoid confusion.

Going forward, REP tokens will contain versioning in their name/symbol on chain so this should be a one-time "fix" for Augur v1 REP.

src/constants/tokens/mainnet.ts

@@ -91,7 +91,7 @@ export default [
   new Token(ChainId.MAINNET, '0x459086F2376525BdCebA5bDDA135e4E9d3FeF5bf', 8, 'renBCH', 'renBCH'),
   new Token(ChainId.MAINNET, '0xEB4C2781e4ebA804CE9a9803C67d0893436bB27D', 8, 'renBTC', 'renBTC'),
   new Token(ChainId.MAINNET, '0x1C5db575E2Ff833E46a2E9864C22F4B22E0B37C2', 8, 'renZEC', 'renZEC'),
-  new Token(ChainId.MAINNET, '0x1985365e9f78359a9B6AD760e32412f4a445E862', 18, 'REP', 'Reputation'),
+  new Token(ChainId.MAINNET, '0x1985365e9f78359a9B6AD760e32412f4a445E862', 18, 'REPv1', 'Augur v1 Reputation'),
   new Token(ChainId.MAINNET, '0x9469D013805bFfB7D3DEBe5E7839237e535ec483', 18, 'RING', 'Darwinia Network Native Token'),
   new Token(ChainId.MAINNET, '0x607F4C5BB672230e8672085532f7e901544a7375', 9, 'RLC', 'iEx.ec Network Token'),
   new Token(ChainId.MAINNET, '0xB4EFd85c19999D84251304bDA99E90B92300Bd93', 18, 'RPL', 'Rocket Pool'),