adjust indentation
speed up hd2str_lua()

It is very slow that evaluating a list of strings with vim.eval().
Evaluate a string instead.
improve hd2str_lua()

Import ichizok's patch:
https://gist.github.com/ichizok/b34b2566ba526116b64a

Use table.insert() and table.concat() instead of concatenating each
byte one by one.
Merge pull request #140 from Shougo/topic/improve-lua

improve hd2str_lua()