cargo-deb looks up README.md in wrong dir when using workspace

[pkolaczk]

I have a multi-crate project with the following structure:

project_root/crate1/README.md
project_root/crate1/Cargo.toml   // with readme = "README.md"
project_root/crate1/src 
project_root/Cargo.toml                // workspace definition

Note there is no README in the project root.

Then I try to build it with:
cargo deb -p crate1

cargo-deb: unable to read extended description from file: README.md
  because: No such file or directory (os error 2)

Creating a symbolic link at the root of the project solves this, which means cargo-deb looks for a top-level README.md, instead of the one associated with the crate selected with -p.

[orhun]

Related #62