only accept either an email or an assertion

routes/device.js

@@ -21,8 +21,8 @@ exports.routes = [
       pre: [ prereqs.assertion, prereqs.userId, prereqs.user ],
       validate: {
         schema: {
-          assertion: Str(),
-          email: Str()
+          assertion: Str().without('email'),
+          email: Str().without('assertion')
         }
       },
       response: {

routes/user.js

@@ -16,8 +16,8 @@ var getConfig = {
   pre: [ prereqs.assertionGet, prereqs.userId, prereqs.user ],
   validate: {
     query: {
-      assertion: Str(),
-      email: Str()
+      assertion: Str().without('email'),
+      email: Str().without('assertion')
     }
   },
   response: {
@@ -38,8 +38,8 @@ exports.routes = [
       pre: [ prereqs.assertion ],
       validate: {
         schema: {
-          assertion: Str(),
-          email: Str()
+          assertion: Str().without('email'),
+          email: Str().without('assertion')
         }
       },
       response: {
@@ -72,8 +72,8 @@ exports.routes = [
       pre: [ prereqs.assertion, prereqs.userId ],
       validate: {
         schema: {
-          assertion: Str(),
-          email: Str()
+          assertion: Str().without('email'),
+          email: Str().without('assertion')
         }
       },
       response: {