Malduck

- Removed strict version pinning from `requirements.txt` where it was not needed (https://github.com/CERT-Polska/malduck/commit/f6d9acaf9ba7a68951b075f305b28390b387c7b5)

Small fixes:
* Fixed Py3-compatibility of `serpent.encrypt`
* `Idamem` is now compatible with IDA 7.4 (>=7.0)

Small improvements related with Py3 support:
- Encoding text-typed (`str`) query argument via `ensure_bytes` was counterintuitive for `ProcessMemory.regexp` and `ProcessMemory.regexv`. If `query` argument is not binary-typed, TypeError exception is raised.
- Fixed issues related with `malduck.main` and configuration extraction engine

Bugfixes:
* `ExtractManager.push_procmem` returned family only for second better config extraction, not for the first one
* `ExtractManager.push_procmem` tried to process embedded binaries even if no Yara matches have been found in whole dump

Breaking changes:
* Refactored `ProcessMemory` regions - part of internally used interface changed a bit. `iter_regions`, `readv_regions` have slightly different argument names and behavior. Lots of corner-cases related with cross-region access have been fixed.
* Static configuration extraction engine has different strategy for processing binaries. Firstly it tries to find as many PE/ELF binaries as possible and extracts configuration using both memory- and file-alignment. Then the best config is chosen based on number of successfully ripped config keys.
* Improved logging (`malduck -v extract`) and exception handling (especially for PE/ELF parse errors)

New features:
* [beta] ProcessMemory interface for IDAPython (`IDAProcessMemory` or `idamem`, tested in IDA Pro >7.0)
* Added `malduck.crypto.aes.AES.encrypt` (but hey, we still need to refactor all these `crypto` things later...)

Bugfixes:
* `malduck.crc32` is guaranteed to return unsigned value both in Py2/Py3

Bugfixes:
- `Extractor.weak` and `Extractor.extractor` must have been placed in particular order
- Improved error handling in `malduck extract` CLI