Allow manifest with byte order mark (BOM)

[andersforsgren]

A cargo .toml file with a byte order mark is a valid UTF-8 encoded file, and should be readable by cargo.

Current behavior (Windows):

failed to parse manifest at `C:\Path\to\Cargo.toml`

Caused by:
  could not parse input as TOML
Cargo.toml:1:1 expected a key but found an empty string

The corresponding issue for the compiler (libsyntax) is rust-lang/rust#12974

cargo --version

cargo 0.4.0-nightly (553b363 2015-08-03) (built 2015-08-03)

[andersforsgren]

Should this perhaps be handled at the parser level in the toml crate? (https://github.com/alexcrichton/toml-rs)

EDIT: I added a PR at toml-rs/toml-rs#75

[alexcrichton]

Thanks for the PR @andersforsgren, I release a new version of toml-rs, would you like to send a PR to update the version Cargo is using?

[alexcrichton]

Ah looks like there's another reason (#2033) to update toml, so I'll just go ahead and do so, thanks again @andersforsgren!