RF(workaround): Disable installing datalad from master in requirement…

….txt

For some reason one of the tests get stuck ATM
datalad_crawler.pipelines.tests.test_simple_with_archives.test_crawl_autoaddtext(True,) ...
when running on travis, and for it, it requires datalad >= 0.11.2 which is
yet to be released.  More information/analysis at
#35 (comment)

requirements.txt

@@ -1 +1,2 @@
-git+https://github.com/datalad/datalad.git
+# TODO: add travis run, at least one or two for testing against master
+# git+https://github.com/datalad/datalad.git