added requirements.txt note
added requirements.txt note

awangga/python-twitter,jquacinella/python-twitter,ligthyear/python-twitter,ryankicks/python-twitter,ryankicks/python-twitter,hethapu/python-twitter,dongguangming/python-twitter,era/python-twitter,jeremylow/python-twitter,WenyingLiu/python-twitter,creeshla/python-twitter,jakeshi/python-twitter,kajarenc/python-twitter,DataBranner/python-twitter,laborautonomo/python-twitter,pathawks/tweet-dump,Vector919/python-twitter,minatverma/python-twitter,datasaurus-rex/python-twitter,laborautonomo/python-twitter,workey-co/python-twitter,shichao-an/python-twitter,laborautonomo/python-twitter,minatverma/python-twitter,minatverma/python-twitter,AnthonyBobsin/python-twitter,numeratechoir/python-twitter,irkru/python-twitter