Put neighbor `lib` to load path if failed to load
Thor doesn't have `run` method
Add option `skip_prepare_build`

This has been used in Build step, but haven't been declared in Script...
Use Bundler.with_clean_env when available

When running `bin/mamiya` with `bundle exec`, bundler assigns some
environment variables. Executing commands in another projects with
hose variables may raise errors around gem system.

For more detail, see: http://bundler.io/v1.3/man/bundle-exec.1.html
Add Script#cd as shorthand of Dir.chdir
Aws::S3 refuses config with keys they don't use
script.build_from is not Pathname
Dir.chdir{..} raises error when chdir within block
Implement mamiya {build,push} command

- Adding some class_options: config,script,application
- Adding some helpers: config,script,storage,_applicasions
- Adding descriptions to supress warning
Update aws-sdk-core from 2.0.0.rc2 to rc6

- AWS' exception classes now has context attributes, so fixing spec to
  follow that specification change.