Switch back to released versions of lettre and lettre_email

Also see rust-lang#1754 where this workaround was originally added.  The changes
were released upstream in version `0.9.2`.

Author: jtgeibel

Cargo.lock

@@ -63,8 +63,8 @@ parking_lot = "0.7.1"
 jemallocator = { version = "0.1.8", features = ['unprefixed_malloc_on_supported_platforms', 'profiling'] }
 jemalloc-ctl = "0.2.0"
 
-lettre = { version = "0.9", git = "https://github.com/lettre/lettre" }
-lettre_email = { version = "0.9", git = "https://github.com/lettre/lettre" }
+lettre = "0.9"
+lettre_email = "0.9"
 failure = "0.1.1"
 
 conduit = "0.8"