Fix calls to get_data() in lesson2 notebook.
Fix calls to get_data() in lesson2 notebook.

Without this change, the get_data() calls fail as described here:

http://forums.fast.ai/t/lesson-2-discussion/161/39

appleby/fastai-courses,kmclaugh/fastai_courses,fastai/courses,nik-hil/fastai,yingchi/fastai-notes,sainathadapa/fastai-courses,organicmatters/Learnfastai,fazzolini/fast_ai,fazzolini/fast_ai,radekosmulski/courses,nik-hil/fastai,asmith26/courses,asmith26/courses,organicmatters/Learnfastai,matsaleh13/courses,benkoo/fast_ai_coursenotes,radekosmulski/courses,fastai/courses,VadimMalykh/courses,appleby/fastai-courses,yingchi/fastai-notes,kmclaugh/fastai_courses,sainathadapa/fastai-courses,VadimMalykh/courses,benkoo/fast_ai_coursenotes,matsaleh13/courses