add git ignore file.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.gitignore

@@ -0,0 +1,23 @@
+*.o
+*.a
+*.so
+
+_obj
+_test
+
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof
+
+coverage.out