Add required error parameter
Merge pull request #11 from tt/fix-example

Fix example
Remove the dependency on loggo.
Merge pull request #12 from howbazaar/remove-loggo-dependency

Remove the dependency on loggo.
Add an ErrorStack method so it can be checked through an interface.
Update docs, add a godoc link.
Rename the ErrorStack method to StackTrace.
Update docs.
Merge pull request #13 from howbazaar/stacktrace-method

Add StackTrace method to the error type