bump rusoto version to 0.15.0, rusoto_codegen dependency to 0.2.2
bump rusoto version to 0.15.0, rusoto_codegen dependency to 0.2.2

mattico/rusoto,rusoto/rusoto,rusoto/rusoto,indiv0/rusoto,DualSpark/rust-aws,mthjones/rusoto,mthjones/rusoto,SecurityInsanity/rusoto,ford-prefect/rusoto,mattico/rusoto,ford-prefect/rusoto,noggleboggle/rusoto,SecurityInsanity/rusoto,DualSpark/rust-aws,DualSpark/rusoto,rusoto/rusoto,DualSpark/rusoto,cmsd2/rusoto,mattico/rusoto,DualSpark/rusoto,DualSpark/rust-aws