py-scrapy: updated to 1.5.1

Scrapy 1.5.1:
This is a maintenance release with important bug fixes, but no new features:
* O(N^2) gzip decompression issue which affected Python 3 and PyPy
  is fixed
* skipping of TLS validation errors is improved
* Ctrl-C handling is fixed in Python 3.5+
* testing fixes
* documentation improvements

(adam)