Add test for document permalink
Solidify document permalink tests
Modify tests a bit
Don't use old `@url` variable

Fix for #2557
Update Maruku dependency to allow use of the latest version.

All Maruku releases post-0.6 follow semver, so they should be backwards-compatible on minor versions. In this case, the only test that needed to change was one that was asserting buggy behavior that was fixed in 0.7.1.
Merge pull request #2575 from alfredxing/test-document-permalink
Update history to reflect merge of #2575 [ci skip]
Merge pull request #2576 from bhollis/maruku-update
Update history to reflect merge of #2576 [ci skip]
Release Jekyll v2.1.1
Finished the Jekyll 2.1.1 release post. [ci skip]
Merge pull request #2564 from jekyll/release-2-1-1
Release 2.1.1