Bump version to 6.7

Includes #176 and #174

Author: dermesser

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "yup-oauth2"
-version = "6.6.0"
+version = "6.7.0"
 authors = ["Sebastian Thiel <[email protected]>", "Lewin Bormann <[email protected]>"]
 repository = "https://github.com/dermesser/yup-oauth2"
 description = "An oauth2 implementation, providing the 'device', 'service account' and 'installed' authorization flows"