Document installation of scrapy via pip
Document installation of scrapy via pip

requirements.txt files was dropped with I22c018149b2eefde6ca5c38c22ac06886fe9a7a8.

Change-Id: I8a3219e2a2ac5fb34172225d3322ea13e21da80d

openstack/openstack-doc-tools,openstack/openstack-doc-tools