- Fix for #207. Previously grep was exiting with 1 and fail build if all
lines from ninja are filtered. Also piping might hide exit code of the
initial command. Now "tee" and "grep" is implemented on python level
and we get exit code of the original command.
- Fixed default value of "scripts_branch", print scripts commit;
- Added option to filter ninja output (on by default as before).
- Copied cache usege reporting and error handling from "master" branch
build to diff checks (useful for debugging).
