Opaque error message on timeout

[chaosflaws]

When uncss times out before a script could be parsed completely, the stack trace contains the error messages Error: Could not load script and Error: request canceled by user. I wasn't aware of the timeout option and spent quite some time digging in the source files tracing down the source of the errors. It would be nice if uncss could provide a clearer error message along the lines of "timeout reached when parsing script ".