core: Allow dots in MIME file types

As reported in https://github.com/tus/tusd/issues/304

get_test.go

@@ -134,8 +134,8 @@ func TestGet(t *testing.T) {
 		store.EXPECT().GetInfo("yes").Return(FileInfo{
 			Offset: 0,
 			MetaData: map[string]string{
-				"filetype": "text/html",
-				"filename": "invoice.html",
+				"filetype": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+				"filename": "invoice.docx",
 			},
 		}, nil)
 
@@ -148,8 +148,8 @@ func TestGet(t *testing.T) {
 			URL:    "yes",
 			ResHeader: map[string]string{
 				"Content-Length":      "0",
-				"Content-Type":        "text/html",
-				"Content-Disposition": `attachment;filename="invoice.html"`,
+				"Content-Type":        "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+				"Content-Disposition": `attachment;filename="invoice.docx"`,
 			},
 			Code:    http.StatusNoContent,
 			ResBody: "",

unrouted_handler.go

@@ -24,7 +24,7 @@ var (
 	reExtractFileID  = regexp.MustCompile(`([^/]+)\/?$`)
 	reForwardedHost  = regexp.MustCompile(`host=([^,]+)`)
 	reForwardedProto = regexp.MustCompile(`proto=(https?)`)
-	reMimeType       = regexp.MustCompile(`^[a-z]+\/[a-z\-\+]+$`)
+	reMimeType       = regexp.MustCompile(`^[a-z]+\/[a-z\-\+\.]+$`)
 )
 
 // HTTPError represents an error with an additional status code attached