Migrate to DuniterPy usage
[DuniterPy](https://git.duniter.org/clients/python/duniterpy)
## Transition plan
- [x] Set Python 3.5 as requirements as DuniterPy 0.52 requires Python 3.5 (DuniterPy 0.60 will requires Python 3.6)
- [x] Keep same behaviours for the commands and the authentication
### Endpoint/GET
- [x] replace GET methods
- [x] Make the code asynchronous
- [x] replace peer document endpoint management
### Commands
- [x] cert:
- [x] replace document generation
- [x] replace sign and post method
- [x] keep `amount` behaviour with authentication
- [x] tx:
- [x] replace document generation
- [x] replace sign and post method
- [x] multi-output
- [ ] #178: intermediaries transactions: infinite loop because of already proceed tx for intermediaries tx.
- [x] `generate_auth_file`
### Authentication
- [x] `scrypt`
- [x] https://git.duniter.org/clients/python/duniterpy/issues/71: add seedhex authentication in DuniterPy: seed in an hexadecimal base with `str` type
- [x] Ğannonce format (PubSec)
- [x] \(E\)WIF (format compatible with Silkaj 0.6)
- #173: Following ticket to implement other methods
### Cleaning
- [x] get rid of no longer needed functions
- [x] `auth.py`: cleaning done. Improvements possible, but later with #77, and #173
- [ ] #177: `network_tools.py`: remove `check_port()`, refactor `best_node()`, `parse_endpoint(s)()`
- [ ] #176: `crypto_tools.py`
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## Code to move to/to implement in DuniterPy
- [x] Authentication methods:
- [x] https://git.duniter.org/clients/python/duniterpy/issues/51, https://git.duniter.org/clients/python/duniterpy/issues/52: WIF/EWIF
- [x] gannonce format: PubSec: https://git.duniter.org/clients/python/duniterpy/issues/51
- [ ] #176: pubkey checksum
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