Opinionated formatter included in the binary

[bmatsuo-at-luthersystems]

The elps executable should contain a fmt command which basically has a subset of the go fmt options.

The parser should be adapted so that it can keep comments and produce an AST that allows it to distinguish whether block comments are attached to an expression or not. That is the following code pieces should not modified and are not equivalent

;; hello

(world)

;; hello
(world)

[bmatsuo-at-luthersystems]

The parser rewrite is also related to #47 and #46 either directly or by extension (depending on the chosen implementation for #46)