Moved constants and storage mixins to immutable directory

contracts/staking/contracts/src/Staking.sol

@@ -18,8 +18,8 @@
 
 pragma solidity ^0.5.9;
 
-import "./core/MixinConstants.sol";
-import "./core/MixinStorage.sol";
+import "./immutable/MixinConstants.sol";
+import "./immutable/MixinStorage.sol";
 import "./core/MixinStake.sol";
 import "./core/MixinPools.sol";
 import "./core/MixinEpoch.sol";

contracts/staking/contracts/src/StakingProxy.sol

@@ -18,7 +18,7 @@
 
 pragma solidity ^0.5.5;
 
-import "./core/MixinStorage.sol";
+import "./immutable/MixinStorage.sol";
 import "./interfaces/IStakingProxy.sol";
 
 

contracts/staking/contracts/src/core/MixinEpoch.sol

@@ -19,7 +19,7 @@
 pragma solidity ^0.5.5;
 
 import "@0x/contracts-utils/contracts/src/SafeMath.sol";
-import "./MixinStorage.sol";
+import "../immutable/MixinStorage.sol";
 import "../interfaces/IStructs.sol";
 
 contract MixinEpoch is

contracts/staking/contracts/src/core/MixinPools.sol

@@ -18,9 +18,9 @@
 
 pragma solidity ^0.5.5;
 
-import "./MixinStorage.sol";
+import "../immutable/MixinStorage.sol";
 import "@0x/contracts-utils/contracts/src/SafeMath.sol";
-import "./MixinConstants.sol";
+import "../immutable/MixinConstants.sol";
 import "../interfaces/IStakingEvents.sol";
 
 contract MixinPools is

contracts/staking/contracts/src/core/MixinStake.sol

@@ -21,8 +21,8 @@ pragma solidity ^0.5.5;
 import "../interfaces/IVault.sol";
 import "../libs/LibZrxToken.sol";
 import "@0x/contracts-utils/contracts/src/SafeMath.sol";
-import "./MixinStorage.sol";
-import "./MixinConstants.sol";
+import "../immutable/MixinStorage.sol";
+import "../immutable/MixinConstants.sol";
 import "../interfaces/IStakingEvents.sol";
 import "./MixinStakeBalances.sol";
 import "./MixinEpoch.sol";

contracts/staking/contracts/src/core/MixinStakeBalances.sol

@@ -21,8 +21,8 @@ pragma solidity ^0.5.5;
 import "../interfaces/IVault.sol";
 import "../libs/LibZrxToken.sol";
 import "@0x/contracts-utils/contracts/src/SafeMath.sol";
-import "./MixinStorage.sol";
-import "./MixinConstants.sol";
+import "../immutable/MixinStorage.sol";
+import "../immutable/MixinConstants.sol";
 import "./MixinEpoch.sol";
 
 

contracts/staking/test/core_test.ts

@@ -100,7 +100,7 @@ describe('Staking Core', () => {
                 expect(currentTimelockPeriod).to.be.bignumber.equal(stakingConstants.INITIAL_TIMELOCK_PERIOD.plus(1));
             }
         });
-        it.only('staking/unstaking', async () => {
+        it('staking/unstaking', async () => {
             ///// 1 SETUP TEST PARAMETERS /////
             const amountToStake = stakingWrapper.toBaseUnitAmount(10);
             const amountToDeactivate = stakingWrapper.toBaseUnitAmount(4);