Change Convertor.client to check for metadata_from.

Previously used source_from didn't work if -s /path/to/file is used without -m local
Add option to create srpm with --srpm
Also logging is redone. When --srpm is used we print logs (info level) into stdout
Avoid situation when LocalFileGetter:self.save_dir is None
Improve --help for pyp2rpm to reflect latest changes.
Don't encode text when write to file.
Decode logging msg from subprocess when on PY3 to avoid b prefix in stdout.
Add basic support for proxy. See --proxy.
Update changelog and bump version number.