Update requirements.txt

[EgorBu]

• hdbscan fails on old versions of numpy
• ValueError: numpy.ufunc size changed, may indicate binary incompatibility scikit-learn-contrib/hdbscan#272

Error log

user@pc:~/hercules/bin$ ./hercules --devs https://github.com/src-d/ml | python3 ../labours.py -m devs
Reading the input... Warning: failed to import yaml.CLoader, falling back to slow yaml.Loader
doneing...                                                                      
Traceback (most recent call last):
  File "../labours.py", line 1581, in <module>
    sys.exit(main())
  File "../labours.py", line 1556, in main
    modes[args.mode]()
  File "../labours.py", line 1532, in devs
    show_devs(args, reader.get_name(), *reader.get_header(), data)
  File "../labours.py", line 1198, in show_devs
    from hdbscan import HDBSCAN
  File "/usr/local/lib/python3.5/dist-packages/hdbscan/__init__.py", line 1, in <module>
    from .hdbscan_ import HDBSCAN, hdbscan
  File "/usr/local/lib/python3.5/dist-packages/hdbscan/hdbscan_.py", line 21, in <module>
    from ._hdbscan_linkage import (single_linkage,
  File "__init__.pxd", line 918, in init hdbscan._hdbscan_linkage
ValueError: numpy.ufunc size changed, may indicate binary incompatibility. Expected 216 from C header, got 192 from PyObject

Signed-off-by: egor egor@sourced.tech

[vmarkovtsev]

Thank you