Update version to 3.6.4
Update release date of 3.6.4 to today
Update Gemfile.lock for nanoc 3.6.4
Make sure dependency tracker stack is empty after failed item rep compilation
Improve handling of index filenames in unified data source
Add more identifier_for_filename tests wrt index
Add dependency tracker stack size sanity check at end of compilation
Merge pull request #330 from nanoc/bug/better-index-filename-handling-in-filesystem-data-sources

Better index filename handling in filesystem data source
Merge pull request #329 from nanoc/bug/dependency-tracker-stack-not-empty-after-error

Dependency tracker stack not empty after error
Update Gemfile.lock
Add release notes for 3.6.5
Update version to 3.6.5
Use Minitest 4.x, not 5+
Update Gemfile.lock
Merge branch 'release-3.6.x' into release-3.x

Conflicts:
	lib/nanoc.rb