fix readme and help

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
In applyPreprocess(), use gcc -E directly is OK

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
[BUG] serious. the insertion like should be more strict. revert for now

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
print message if purging a preprocessed file failed

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
try-finally in applyPreprocessing()

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>