@0x/types: Add FillResults, MatchedFillResults, and

`BatchMatchedFillResults` types.
`@0x/contracts-utils`: Add reference functions for `SafeMath`.
`@0x/contracts-exchange-libs`: Add reference functions for `LibMath` and
`LibFillResults`.
`@0x/contracts-test-utils`: Move `*FillResults` types to `@0x/types`.
`@0x/contracts-test-utils`: Add `log_utils.ts`.
`@0x/contracts-test-utils`: Add `hexRandom()` to `hex_utils.ts`.
`@0x/contracts-test-utils`: Add the contstants: `MAX_UINT256`,
`ADDRESS_LENGTH`.

contracts/utils/src/reference_functions.ts

@@ -0,0 +1,44 @@
+import { AnyRevertError, BigNumber, SafeMathRevertErrors } from '@0x/utils';
+
+const MAX_UINT256 = new BigNumber(2).pow(256).minus(1);
+
+export function safeAdd(a: BigNumber, b: BigNumber): BigNumber {
+    const r = a.plus(b);
+    if (r.isGreaterThan(MAX_UINT256)) {
+        throw new SafeMathRevertErrors.SafeMathError(
+            SafeMathRevertErrors.SafeMathErrorCodes.Uint256AdditionOverflow,
+            a,
+            b,
+        );
+    }
+    return r;
+}
+
+export function safeSub(a: BigNumber, b: BigNumber): BigNumber {
+    const r = a.minus(b);
+    if (r.isLessThan(0)) {
+        throw new SafeMathRevertErrors.SafeMathError(
+            SafeMathRevertErrors.SafeMathErrorCodes.Uint256SubtractionUnderflow,
+            a,
+            b,
+        );
+    }
+    return r;
+}
+
+export function safeMul(a: BigNumber, b: BigNumber): BigNumber {
+    const r = a.times(b);
+    if (r.isGreaterThan(MAX_UINT256)) {
+        // Solidity implementation does not throw a reason.
+        throw new AnyRevertError();
+    }
+    return r;
+}
+
+export function safeDiv(a: BigNumber, b: BigNumber): BigNumber {
+    if (b.isEqualTo(0)) {
+        // Solidity implementation does not throw a reason.
+        throw new AnyRevertError();
+    }
+    return a.dividedToIntegerBy(b);
+}