added spec for rendering right templates depending on passed in  params
added responds to 'set_identifier' spec for Certificate
Merge pull request #4 from AgileVentures/tests

Updates in code
Merge branch 'master' of https://github.com/AgileVentures/certificates into tests
added testing of 'write_to_cert' method
failing specs in 'av_cert_spec.rb'
Fixed tests