properly use non-localhost BaseUrl in server command
Gofmt

Command: `gofmt -l -s -w .`
Fixes #141: Wrong section in multi level structure
Testcases for multilevel structure were wrong
Section in example was wrong for happiness.md
Added PageSorter and PagesByDate
Complete refactor of indexes, move (and rewrite) page sorting to page.go, add tests
Added documentation on ordering indexes, content and content within indexes