Added some additional error info when parsing version constraints, see issue https://github.com/Olivine-Labs/busted/issues/169
fixed return value
Off-by-one fix sent by Philipp Janda
Fix error affecting `luarocks make`, as reported by Ignacio Burgueño
fixed bad varname
Merge pull request #137 from Tieske/additional_error_info

Added some additional error info when parsing version constraints