Code#to_s: standardise method chain

Make it as in `Code#raw` (they both do similar things).

And fix typos, typos, typos.

Signed-off-by: Kyrylo Silin <kyrylosilin@gmail.com>
Use `block` instead of `blk` across-the-board

Everywhere else in the code it's the very `block`.

Rename `Code#get_abs_path` to `#abs_path`.

Signed-off-by: Kyrylo Silin <kyrylosilin@gmail.com>