Add a Travis config.
Trying out an experimental OS option for OS X.

See https://github.com/sbt/sbt-native-packager/commit/7ec2b16a712f856cfbe8bb541f60b103b42301a9
See https://github.com/travis-ci/travis-ci/issues/216
Move the functions to get errno into their own file.

This is needed to populate the autodie::exception object.  I picked
the code from making $! to best simulate how the Perl code does it.

This function would probably be useful to normalize all the ways
errno is accessed in the code, possibly splitting it into a function
to get the number and string parts.
Put autodie into truncate().

This is an experiment to get it working.  The code now hard coded in truncate will
later be moved into functions for use elsewhere.

* truncate has been removed from autodie.pm.  That should probably be
  conditional based on the Perl version.
* ok !eval { use autodie; truncate(...) } is erroring, need to figure that out.
* Much of the code here will be put into subroutines.
* caller, file, line and package cannot be passed into autodie::exception
  and it's getting the calling routine wrong.