Relax minium object size limit, one can really upload a 0byte file

For example
~~~
$ mc ls https://s3.amazonaws.com/ferenginar/test.go
[2015-05-23 12:02:06 PDT]     0B test.go

$ curl -i -X HEAD https://s3.amazonaws.com/ferenginar/test.go
HTTP/1.1 200 OK
x-amz-id-2: ZMWLriPH+uQJ8IsaMHmuNOU/FXvdSq+s6O7ugUI9hZ695XJTNAZ1utKxh03w5Jcf
x-amz-request-id: F5A11F533B74DD8F
Date: Sat, 23 May 2015 19:19:29 GMT
Last-Modified: Sat, 23 May 2015 19:02:06 GMT
ETag: "d41d8cd98f00b204e9800998ecf8427e"
Accept-Ranges: bytes
Content-Type: binary/octet-stream
Content-Length: 0
Server: AmazonS3
~~~

pkg/api/api_object_handlers.go

@@ -168,10 +168,19 @@ func (server *minioAPI) putObjectHandler(w http.ResponseWriter, req *http.Reques
 		return
 	}
 	/// minimum Upload size for objects in a single operation
-	if isMinObjectSize(size) {
-		writeErrorResponse(w, req, EntityTooSmall, acceptsContentType, req.URL.Path)
-		return
-	}
+	//
+	// Surprisingly while Amazon in their document states that S3 objects have 1byte
+	// as the minimum limit, they do not seem to enforce it one can successfully
+	// create a 0byte file using a regular putObject() operation
+	//
+	// For example take a look at :-
+	//
+	//   $ mc ls https://s3.amazonaws.com/ferenginar/test.go
+	//
+	// if isMinObjectSize(size) {
+	//      writeErrorResponse(w, req, EntityTooSmall, acceptsContentType, req.URL.Path)
+	//	return
+	// }
 	sizeInt64, err := strconv.ParseInt(size, 10, 64)
 	if err != nil {
 		writeErrorResponse(w, req, InvalidRequest, acceptsContentType, req.URL.Path)
@@ -275,15 +284,6 @@ func (server *minioAPI) putObjectPartHandler(w http.ResponseWriter, req *http.Re
 		return
 	}
 
-	// last part can be less than < 5MB so we need to figure out a way to handle it first
-	// and then enable below code (y4m4)
-	//
-	/// minimum Upload size for multipart objects in a single operation
-	//	if isMinMultipartObjectSize(size) {
-	//		writeErrorResponse(w, req, EntityTooSmall, acceptsContentType, req.URL.Path)
-	//		return
-	//	}
-
 	sizeInt64, err := strconv.ParseInt(size, 10, 64)
 	if err != nil {
 		writeErrorResponse(w, req, InvalidRequest, acceptsContentType, req.URL.Path)