Auto merge of #2344 - Stebalien:upgrade-term, r=alexcrichton

This PR re-upgrades term to 0.4.3. Cargo now detects whether or not
color is supported immediately after creating the TerminfoTerminal.

Backstory:

Before v0.4, term used to return `Ok(true)` if something succeeded,
`Ok(false)` if the operation was unsupported, and `Err(io::Error)` if there
was an IO error. Now, it returns `Ok(())` if the operation succeeds and
`Err(term::Error)` if the operation fails. If the operation is unsupported,
it returns `Err(term::Error::NotSupported)`. This means that, if `op` is
unsupported, `try!(term.op())` will now return an error instead of silently
failing (well, return false but that's effectively silent).

Fixes #2338.