Fix following removal of Attribute.value (#136)
Fix following removal of Attribute.value (#136)

Since rust-lang/rust#40346 has now been merged, Attribute no longer has
a .value field. Instead, we must follow the token stream and modify the
tokens directly. For Docstring attributes, there should only be one
token, the docstring value.
ms705/tarpc,tikue/tarpc,google/tarpc,ms705/tarpc,tikue/tarpc,google/tarpc