Added download operation and queue to importer.
Merge branch 'master' of https://github.com/TEDxCT/tedx_ios

# By Victor Kirov (3) and Daniel Galasko (1)
# Via Daniel Galasko (1) and Victor Kirov (1)
* 'master' of https://github.com/TEDxCT/tedx_ios:
  Added genre to talks Fixed constraints on talk screen
  Made talk screen data driven
  Made Agenda data driven
  added identifier to speaker