bump pa11ycrawler version to v1.5.8

[pa11ycrawler] enable load_courses from CLI

force pa11ycrawler to run

[pa11ycrawler] bump version to 1.5.5

move around some paver opts

crawl -> test

bump to v1.5.8

let's stick to crawl for now

Changing dash to underscore in skip-fetch

revert a couple of options

add back $RUN_PA11YCRAWLER check

requirements/edx/base.txt

@@ -170,7 +170,7 @@ nose-exclude
 nose-ignore-docstring
 nose-randomly==1.2.0
 nosexcover==1.0.7
-pa11ycrawler==1.5.4
+pa11ycrawler==1.5.8
 pep8==1.5.7
 PyContracts==1.7.1
 python-subunit==0.0.16