Adding a test case for post bindings and improving error message

collects/tests/web-server/pr/post-binding.rkt

@@ -0,0 +1,16 @@
+#lang racket/base
+(require web-server/http
+         web-server/http/request
+         web-server/http/bindings
+         rackunit
+         "../util.rkt")
+
+(define request-bs
+  #"POST /xapps/agent-stat HTTP/1.1\r\nUser-Agent: curl/7.21.6 (x86_64-pc-linux-gnu) libcurl/7.21.6 OpenSSL/1.0.0e zlib/1.2.3.4 libidn/1.22 librtmp/2.3\r\nHost: localhost:8080\r\nAccept: */*\r\nContent-Length: 25\r\nContent-Type: application/x-www-form-urlencoded\r\n\r\nstat=testing%20via%20curl")
+
+(define-values (conn ip op)
+  (make-mock-connection request-bs))
+(define-values (req close?)
+  (read-request conn 80 (λ _ (values "to" "from"))))
+(check-equal? (request-bindings req)
+              (list (cons 'stat "testing via curl")))