Add sftp_attributes structure to api.
Add more api methods.
Partial refactor of sftp module for more checks for file transferrs methods.
Shell class now implements contexmanager protocol.
Remove wrong __all__ variable from api module.
Refactorized __init__ module.
Add to_text method to compat module with other minor fixes.
Minor changes on exception hierarchy.
Now session has lazy connection management.
Add -Xfaulthandler to runtests command line.
Adapt tests to last changes.
Minor changes on sftp module.
Exception management improvements on sftp module.