Loosen thor dependency. #20.

Bcdatabase seems to work fine with the latest thor (0.17.0). Let's
assume semver for now.

Suggested by @asmega.
Version 1.2.3.
Update for ongoing development.
.rvmrc => .ruby-version/.ruby-gemset
Removing activesupport dependency. #21

I18n (dependency of activesupport) prints a deprecation message
when enforce_available_locales is not configured, which is annoying
for apps not using I18n. Since we are only using activesupports'
Array#extract_options! method we decided to inline it into bcdatabase
and remove the activesupport dependency.
Merge pull request #21 from NUBIC/21-remove_activesupport_dependency

Removing activesupport dependency. #21
Version 1.2.4
Prep for ongoing development.