Things I did while unable to commit

- Log rotation
- Execution cancellation
- HTTP redirect, error functions
- Changed naming of document parsing/loading functions

error.go

@@ -3,6 +3,7 @@ package step
 // Error enumerates errors common to this package.
 type Error string; const (
 	ErrCircularInheritance  Error = "circular inheritance"
+	ErrExecutionCanceled    Error = "execution canceled"
 	ErrMetaMalformed        Error = "metadata is malformed"
 	ErrMetaNeverClosed      Error = "metadata is never closed"
 	ErrTypeMismatch         Error = "type mismatch"