Compilation issue on windows for 0.8.0 version

[dkijania]

when compiling on windows, got compilation error:

error[E0433]: failed to resolve: could not find `Error` in `{{root}}`
  --> C:\Users\Dariusz\.cargo\registry\src\github.com-1ecc6299db9ec823\grpc-0.8.0\src\client_stub.rs:59:15
   |
59 |         Err(::Error::Other("new_plain_unix unsupported"))
   |               ^^^^^ could not find `Error` in `{{root}}`
For more information about this error, try `rustc --explain E0433`.
error: could not compile `grpc`.

fix: client_stub.rs:59

- Err(::Error::Other("new_plain_unix unsupported"))
+ Err(crate::Error::Other("new_plain_unix unsupported"))

[stepancheg]

Published 0.8.1 with fix. Thanks!