Write tests for `set!` analyzer.
Write tests for `do` analyser.
Update analyser API to be more consistent.
Fix `def analyser` and write tests for it.
Only export if top level scope.
Some work on `let*` analyzer.
Little refactoring to improve naming.
Get rid off the `:meta` properties from analysed forms.
Add support for `loop` forms.
Remove redundant argument.
Make `:statements` value `nil` if no statements are necessary.
Add more docs.
Implement `fn` analyzer.