add writable collections to sitemap output
add tests for custom permalinks
Use `post.last_modified_at` for post lastmod
Merge pull request #37 from pathawks/last_modified_at
Update history to reflect merge of #37 [ci skip]
Merge pull request #30 from sankage/collections
Update history to reflect merge of #30 [ci skip]
Add note about precedence. Closes #17.
update history to reflect release of 0.5.1
update history to reflect relase of 0.6.0
:gem: version bumped to 0.6.0