Add a utility library for convenience methods

Add tests for utils

Update changes
Fixup a bad C< for my  qw(  ) > unwrapped qw()
remove a useless check

if $line is empty, we have already exited the while loop
add generic support for multiline header fields

the %method_map hash is used to provide method mapping and a description
of the transformation from the list of string to the actual attribute

also drop the loop on all the values for a given key

using split / / instead of split ' ' keeps the initial empty fields
that are needed for properly detecting the continuation lines
add support for the gpgsig field in commits

using the same attribute name as kentfredric in #3

closes #3
add support for mergetag in commits

closes #4