Add source-map module to dependencies

Fixes #4268

package.json

@@ -91,6 +91,7 @@
     "recursive-copy": "2.0.6",
     "resolve": "1.5.0",
     "send": "0.16.1",
+    "source-map": "0.7.2",
     "strip-ansi": "3.0.1",
     "styled-jsx": "2.2.6",
     "touch": "3.1.0",

yarn.lock

@@ -6772,6 +6772,10 @@ source-map@0.6.1, source-map@^0.6.1, source-map@~0.6.1:
   version "0.6.1"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
 
+source-map@0.7.2:
+  version "0.7.2"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.7.2.tgz#115c3e891aaa9a484869fd2b89391a225feba344"
+
 source-map@^0.4.4:
   version "0.4.4"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.4.4.tgz#eba4f5da9c0dc999de68032d8b4f76173652036b"