- remove usage of "attr.s" across the code
- make msg.set_file() copy a file into blobdir if it isn't already
- regroup tests
- add set_draft/get_draft API
* import python, try to adapt for rust
* add missing wrapper functions
* - try to write up how to build python bindings
- strike some unused functions from deltachat.h
* adjustments to make tox work
* try to run circle-ci with python build
* don't do docs
* running cargo test as well
* don't run cargo test anymore, that's done in other ci jobs
* also build docs
* don't run doxygen anymore
* subst C with Rust
* a try to get better wheels
Closes#41
