vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/google.golang.org/api/adexperiencereport/v1/adexperiencereport-api.json

@@ -163,7 +163,7 @@
       }
     }
   },
-  "revision": "20180129",
+  "revision": "20180420",
   "rootUrl": "https://adexperiencereport.googleapis.com/",
   "schemas": {
     "PlatformSummary": {
@@ -243,7 +243,7 @@
       "type": "object"
     },
     "SiteSummaryResponse": {
-      "description": "Response message for GetSiteSummary.",
+      "description": "Response message for GetSiteSummary.\nDo not confuse with same message in google.chrome.abusiveexperiencereport.v1",
       "id": "SiteSummaryResponse",
       "properties": {
         "desktopSummary": {
@@ -277,7 +277,7 @@
     }
   },
   "servicePath": "",
-  "title": "Google Ad Experience Report API",
+  "title": "Ad Experience Report API",
   "version": "v1",
   "version_module": true
 }

vendor/google.golang.org/api/adexperiencereport/v1/adexperiencereport-gen.go

@@ -1,4 +1,4 @@
-// Package adexperiencereport provides access to the Google Ad Experience Report API.
+// Package adexperiencereport provides access to the Ad Experience Report API.
 //
 // See https://developers.google.com/ad-experience-report/
 //
@@ -164,6 +164,8 @@ func (s *PlatformSummary) MarshalJSON() ([]byte, error) {
 }
 
 // SiteSummaryResponse: Response message for GetSiteSummary.
+// Do not confuse with same message in
+// google.chrome.abusiveexperiencereport.v1
 type SiteSummaryResponse struct {
 	// DesktopSummary: Summary for the desktop review of the site.
 	DesktopSummary *PlatformSummary `json:"desktopSummary,omitempty"`