Update flow and use flow-typed; fill in gaps introduced (#121)

This updates react-docgen to use the latest version of flow. It also
moves our libdefs to a directory called flow-typed, which is now a
common convention (see flowtype/flow-typed). It also fills in a couple
of gaps introduced by updating to the latest flow.

Author: wbinnssmith

.flowconfig

@@ -4,6 +4,5 @@
 [include]
 
 [libs]
-flow/
 
 [options]

flow/react-docgen.js renamed to flow-typed/react-docgen.js

@@ -47,7 +47,7 @@
     "babel-preset-stage-1": "^6.5.0",
     "cross-spawn": "^4.0.0",
     "eslint": "^3.2.2",
-    "flow-bin": "^0.30.0",
+    "flow-bin": "^0.31.0",
     "jest-cli": "^14.1.0",
     "rimraf": "^2.3.2",
     "temp": "^0.8.1"

flow/recast.js renamed to flow-typed/recast.js

@@ -104,6 +104,10 @@ function returnsJSXElementOrReactCreateElementCall(path) {
         if (resolvedValue && types.ObjectExpression.check(resolvedValue.node)) {
           var resolvedMemberExpression = namesToResolve
             .reduce((result, path) => { // eslint-disable-line no-shadow
+              if (!path) {
+                return result;
+              }
+
               if (result) {
                 result = getPropertyValuePath(result, path.node.name);
                 if (result && types.Identifier.check(result.node)) {
@@ -113,7 +117,10 @@ function returnsJSXElementOrReactCreateElementCall(path) {
               return result;
             }, resolvedValue);
 
-          if (returnsJSXElementOrReactCreateElementCall(resolvedMemberExpression)) {
+          if (
+            !resolvedMemberExpression ||
+            returnsJSXElementOrReactCreateElementCall(resolvedMemberExpression)
+          ) {
             visited = true;
             return false;
           }