Replace deep-extend with merge from lodash (MetaMask#7908)

The `merge` function from `deep-extend` is at least mostly equivalent
to `merge` from `lodash` - certainly in how we're using it.

app/scripts/migrations/009.js

@@ -6,7 +6,7 @@ This migration breaks out the CurrencyController substate
 
 */
 
-import merge from 'deep-extend'
+import { merge } from 'lodash'
 
 import clone from 'clone'
 

app/scripts/migrations/010.js

@@ -6,7 +6,7 @@ This migration breaks out the ShapeShiftController substate
 
 */
 
-import merge from 'deep-extend'
+import { merge } from 'lodash'
 
 import clone from 'clone'
 

package.json

@@ -97,8 +97,8 @@
     "bip39": "^2.2.0",
     "bn.js": "^4.11.7",
     "browserify-derequire": "^0.9.4",
-    "cfx-fc-abi": "^1.0.0",
     "c3": "^0.7.10",
+    "cfx-fc-abi": "^1.0.0",
     "classnames": "^2.2.6",
     "clone": "^2.1.2",
     "content-hash": "^2.5.0",
@@ -107,7 +107,6 @@
     "d3": "^5.15.0",
     "debounce": "1.1.0",
     "debounce-stream": "^2.0.0",
-    "deep-extend": "^0.5.1",
     "deep-freeze-strict": "1.1.1",
     "detect-node": "^2.0.3",
     "dnode": "^1.2.2",

yarn.lock

@@ -9116,7 +9116,7 @@ deep-equal@^1.1.0:
     object-keys "^1.1.1"
     regexp.prototype.flags "^1.2.0"
 
-deep-extend@^0.5.0, deep-extend@^0.5.1:
+deep-extend@^0.5.0:
   version "0.5.1"
   resolved "https://registry.yarnpkg.com/deep-extend/-/deep-extend-0.5.1.tgz#b894a9dd90d3023fbf1c55a394fb858eb2066f1f"
   integrity sha512-N8vBdOa+DF7zkRrDCsaOXoCs/E2fJfx9B9MrKnnSiHNh4ws7eSys6YQE4KvT1cecKmOASYQBhbKjeuDD9lT81w==