issue #19

[latticetower]

wrote one of possible problem solutions - added calls to ::Plotrb::Base.classify method to Mark and Scale classes (to camelcase field names), fixed tests. Another solution would be to remove classify methods from base.rb completely (it turned out that this method also downcases first letter, so after removing camelcase problem remains until this is also removed, thus making classify method useless).

[agarie]

@zuhao Please take a look.