(#119) Restore backward compatibility with Sinatra 1.2

This is a fix for:
http://code.google.com/p/rubycas-server/issues/detail?id=119

Prior to this commit, rubycas-server was not compatible with Sinatra
1.2 even though the rubycas-server.gemspec file claimed it was. With
this commit, lib/casserver/server.rb distinguishes between the :public
and :public_folder setting. The former is for use with Sinatra 1.3,
the latter with Sinatra 1.2.

This has been tested with Sinatra 1.2.6.
(#118) Relax bundler requirement

Prior to this commit, rubycas-server depended on the bundler gem even
in environments in which the necessary dependencies are already met,
such as some production environments. This forces users to
unnecessarily install bundler, which isn't an option in many
restrictive production environments. With this commit, the bundler
dependency is relaxed so that a failure to load bundler doesn't result
in failure, but rather allows execution to continue under the
assumption that the necessary dependencies are already in place. This
commit should not change any behavior in environments where bundler is
available.
(#120) Remove unnecessary BCrypt dependency

See issue http://code.google.com/p/rubycas-server/issues/detail?id=120

Prior to this commit, the SQLEncrypted authenticator required the
bcrypt gem but never made use of it. This commit removes this
dependency.
Removed Gettext support and added internationalization support using R18n library.
Renamed locales directory
Convert all .po file to .yml to work with R18n
Fix views to work with new localization structure
fixed bug where authentication could proceed even with an invalid login ticket (thanks @joe81)
Merge pull request #84 from lifton/issue/120/remove-extraneous-dependency

(#120) Remove unnecessary BCrypt dependency
Merge pull request #83 from lifton/issue/118/ease-bundler-requirement

(#118) Relax bundler requirement
Merge pull request #81 from lifton/issue/119/restore-sinatra-backward-compatibility

(#119) Restore backward compatibility with Sinatra 1.2
Merge pull request #92 from mitfik/rubycas-server

---

I fix branch with r18n support for server.

- convert all .po file to yml files
- provide new yml structure (I think this one is much more clear for translators, because base on context when this text appear)
- rename `i18n` to `locales` which is more common
- remove po directory with all files
small change to translation file structure and key name typo fix
username and password labels in login form are now right-aligned
adapted RackTest external redirect monkeypatch to work with Capybara 1.1.2
lock to Capybara 1.1.2 since future versions are likely to break monkeypatch in spec_helper.rb
adapted localization specs to work with new R18n-based localization system
changed my mind about the naming of success_ strings
regenerated Gemfile.lock for 1.1.0
updated CHANGELOG and gemspec for 1.1.0