Drop respec? check

The pivotal/jasmine-gem dropped support for Rspec 2 and therefore the `rspec2?` method in the Dependencies module. At it stands, using specs that use phantom_jasmine die with:

rake aborted!
undefined method `rspec2?' for Jasmine::Dependencies:Module
/Users/larslevie/.rvm/gems/ruby-2.1.0@mineralist/gems/phantom_jasmine-0.1.0/lib/tasks/phantom_jasmine.rake:4:in `block (2 levels) in <top (required)>'
/Users/larslevie/.rvm/gems/ruby-2.1.0@mineralist/bin/ruby_executable_hooks:15:in `eval'
/Users/larslevie/.rvm/gems/ruby-2.1.0@mineralist/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => parallel:spec => jasmine:phantom