remove a double definition of exceptions

These exceptions are already defined in exceptions.rb, so I think they shouldn't be defined in entry.rb.

I didn't try to manually figure out if this might break anything, but all tests pass.
Do not unshift ourselves on the $LOADPATH since we now use require_relative

no need to touch it and bad practice anyways
Merge pull request #6 from najamelan/hotfix/cleanup

Remove some perl-style requirements.