Add `codefromstrings` option.
This config option allows to override the behavior
in which 'source' entries that do not begin with '@'
are ignored. This is done to skip code loaded from
(often dynamically-generated) strings, but some
applications use their own loaders and do not add
'@' like the standard Lua interpreter.
Closes #15.
Update README.md
Fix. Do not remove first letter from file name when codefromstring is true.