Replace lodash curry with our own

lodash's curry is great and does a lot, but we don't need it all. This
is quite a bit faster.

Currently, it does away with placeholder support.

updeep curry partial call x 9,951,410 ops/sec ±1.61% (62 runs sampled)
lodash curry partial call x 988,949 ops/sec ±1.36% (62 runs sampled)

lib/if.js

@@ -0,0 +1,6 @@
+import ifElse from './ifElse';
+import curry from './util/curry';
+
+export default curry((predicate, trueUpdates, object) =>
+  ifElse(predicate, trueUpdates, {}, object)
+);

lib/index.js

@@ -1,5 +1,6 @@
 import freeze from './freeze';
 import is from './is';
+import _if from './if';
 import ifElse from './ifElse';
 import map from './map';
 import omit from './omit';
@@ -8,11 +9,9 @@ import update from './update';
 import updateIn from './updateIn';
 import withDefault from './withDefault';
 
-import { placeholder as _ } from 'lodash/function/curry';
-
 const u = update;
 
-u.if = ifElse(_, _, {});
+u.if = _if;
 u.ifElse = ifElse;
 u.is = is;
 u.freeze = freeze;

lib/is.js

@@ -1,5 +1,5 @@
 import splitPath from './util/splitPath';
-import curry from 'lodash/function/curry';
+import curry from './util/curry';
 
 function is(path, predicate, object) {
   const parts = splitPath(path);

lib/update.js

@@ -75,4 +75,4 @@ function update(updates, object, ...args) {
   return { ...object, ...resolvedUpdates };
 }
 
-export default wrap(update);
+export default wrap(update, 2);

lib/updateIn.js

@@ -1,4 +1,4 @@
-import curry from 'lodash/function/curry';
+import curry from './util/curry';
 import update from './update';
 import splitPath from './util/splitPath';
 

lib/util/curry.js

@@ -28,3 +28,25 @@ export function curry3(fn) {
     return curried;
   };
 }
+
+export function curry4(fn) {
+  return function curried(a, b, c, d, e, f) {
+    const n = arguments.length;
+
+    if (n >= 4) return fn(a, b, c, d, e, f);
+    if (n === 3) return curry1((d, e, f) => fn(a, b, c, d, e, f));
+    if (n === 2) return curry2((c, d, e, f) => fn(a, b, c, d, e, f));
+    if (n === 1) return curry3((b, c, d, e, f) => fn(a, b, c, d, e, f));
+    return curried;
+  };
+}
+
+export default function curry(fn, length = fn.length) {
+  return [
+    fn,
+    curry1,
+    curry2,
+    curry3,
+    curry4,
+  ][length](fn);
+}

lib/withDefault.js

@@ -1,5 +1,5 @@
 import update from './update';
-import curry from 'lodash/function/curry';
+import curry from './util/curry';
 
 function withDefault(defaultValue, updates, object) {
   if (typeof object === 'undefined') {

lib/wrap.js

@@ -1,4 +1,4 @@
-import curry from 'lodash/function/curry';
+import curry from './util/curry';
 import freeze from './freeze';
 
 export default function wrap(func, length = func.length) {