Add docstrings and follow up on some conventions

[volrath]

A few things to notice:

• In parseclj.el:
  • I moved parseclj--leaf-tokens and parseclj--closing-tokens to parseclj-lex.el, since tokens are lexical structures.
  • I moved parseclj--string, parseclj--character and parseclj--leaf-token-value to parseedn.el. Reasoning behind it is that these function produce emacs lisp values, which goes with everything else in parseedn.
  • I changed error messages. Initially I changed them because they were generating checkdoc warnings (format-message messages should start with capital letters, and I didn't think parseclj: should be capitalized.) After reading through the Signaling Errors documentation, I started thinking that maybe we should take a different approach with the way we are signaling. Maybe instead of providing a single string message, we provide a tuple of position (int) and message (str). This way is more similar to other errors like wrong-type-argument or wrong-number-of-arguments. Also, documentation says that:

If the error is not handled, the two arguments are used in printing the error message. Normally, this error message is provided by the error-message property of error-symbol.

And parseclj-parse-error's message is already "parseclj: Syntax Error". But I'm not 100% sure if this covers everything we want from an error message.

• In parseclj-ast.el:
  • I moved unparsing functions to this file and removed parseclj-unparse. These functions are only for unparsing our AST data structure definition anyway.

[volrath]

Is this true? not entirely sure. If it isn't, maybe we should add a t clause at the end that catches possible errors.

[volrath]

Intentionally left this one blank. Not quite sure I understand everything going on here and I thought it was better to ask you for clarification. Maybe we could add some one-line comments to each of the replace-regexp-strings as well.

[volrath]

I'm not really happy with this docstring, I feel it should have a little bit more content, but I'm not sure what else to put here. thoughts?

[volrath]

Some other extra comments.

[volrath]

According to our conversation yesterday, I moved the shift/reduce parser to its own module. Called it parseclj-parser.el as a provisional name, just let me know if you are ok with it.

I also moved the --leaf-token-value from parseedn to parseclj-lex, where I think it fits nicely because it's a lexical token function. But it might also work in parseclj-parser.

Now parseedn can be ran standalone, only depending on parseclj-parser and a. No other library depends on parseedn either.