* New rule: line-length-limit
* simplify the panic message of rule line-length-limit
* Refactors `line-length-limit` rule, use private `check` method instead of `Visit`
* Adds rule superfluous-else (an extension of indent-error-flow)
* initial (non functional) version
* empty-block working version
* adds tests for empty-block rule
* Adds empty-block to the rules table
* code clean-up