add error handling for form

services/web/app/views/subscriptions/plans.pug

@@ -231,7 +231,9 @@ block content
 										input(ng-model="form.source", type="hidden", ng-init="form.source = '__ref__'; form.subject = 'General enquiry for larger ShareLaTeX use';")
 									.form-group.text-center
 										input#saveForm.btn-success.btn.btn-lg(name='saveForm', type='submit', ng-disabled="sending",  value='Request a quote')
-								span(ng-show="sent")
+								span(ng-show="sent && error")
+									p Error sending request.
+								span(ng-show="sent && error == false")
 									p Request Sent, Thank you.
 
 				.row

services/web/public/coffee/main/contact-us.coffee

@@ -79,6 +79,7 @@ define [
 		$scope.form = {}
 		$scope.sent = false
 		$scope.sending = false
+		$scope.error = false
 		$scope.contactUs = ->
 			if !$scope.form.email?
 				console.log "email not set"
@@ -97,4 +98,5 @@ define [
 			request = $http.post "/support", data
 			request.then (response)->
 				$scope.sent = true
+				$scope.error = (response.status != 200)
 				$scope.$apply()