Add CRLF character to end of multipart body.

Per RFC 2046 there is an optional CRLF character at the end
of the multipart-body to delimit between the body and optional
epilogue. Some server implementations break if this character is
not added.

lib/http/form_data/multipart.rb

@@ -52,7 +52,7 @@ def glue
 
       # @return [String]
       def tail
-        @tail ||= "--#{@boundary}--"
+        @tail ||= "--#{@boundary}--#{CRLF}"
       end
     end
   end

spec/lib/http/form_data/multipart_spec.rb

@@ -26,7 +26,7 @@ def disposition(params)
         "#{disposition 'name' => 'baz', 'filename' => file.filename}#{crlf}",
         "Content-Type: #{file.content_type}#{crlf}",
         "#{crlf}#{file}#{crlf}",
-        "--#{boundary_value}--"
+        "--#{boundary_value}--#{crlf}"
       ].join("")
     end
 
@@ -44,7 +44,7 @@ def disposition(params)
           "#{disposition 'name' => 'baz', 'filename' => file.filename}#{crlf}",
           "Content-Type: #{file.content_type}#{crlf}",
           "#{crlf}#{file}#{crlf}",
-          "--my-boundary--"
+          "--my-boundary--#{crlf}"
         ].join("")
       end
     end
@@ -61,7 +61,7 @@ def disposition(params)
           "#{disposition 'name' => 'foo'}#{crlf}",
           "Content-Type: #{part.content_type}#{crlf}",
           "#{crlf}s#{crlf}",
-          "--#{boundary_value}--"
+          "--#{boundary_value}--#{crlf}"
         ].join("")
       end
     end
@@ -77,7 +77,7 @@ def disposition(params)
           "--#{boundary_value}#{crlf}",
           "#{disposition 'name' => 'foo'}#{crlf}",
           "#{crlf}s#{crlf}",
-          "--#{boundary_value}--"
+          "--#{boundary_value}--#{crlf}"
         ].join("")
       end
     end