Auto merge of #4595 - treiff:update-appveyor-badge-documentation, r=alexcrichton
Auto merge of #4595 - treiff:update-appveyor-badge-documentation, r=alexcrichton

Update docs for appveyor badge.

Can now optionally specify the appveyor `project_name`.

Related PR: [rust-lang/crates.io#1111](https://github.com/rust-lang/crates.io/pull/1111)
Related Issue: [rust-lang/crates.io#587](https://github.com/rust-lang/crates.io/issues/587)

tsurai/cargo,achanda/cargo,tshepang/cargo,tsurai/cargo,vojtechkral/cargo,tsurai/cargo,tshepang/cargo,rustyhorde/cargo,rustyhorde/cargo,eminence/cargo,nipunn1313/cargo,vojtechkral/cargo,tshepang/cargo,vojtechkral/cargo,eminence/cargo,eminence/cargo,achanda/cargo,rustyhorde/cargo,tsurai/cargo,nipunn1313/cargo,rust-lang/cargo,achanda/cargo,achanda/cargo,vojtechkral/cargo,tsurai/cargo,rust-lang/cargo,rustyhorde/cargo,nipunn1313/cargo,nipunn1313/cargo,tshepang/cargo,rust-lang/cargo,eminence/cargo,rust-lang/cargo