Fixed a str-int concat bug in gen_feats.py
Fixed a str-int concat bug in gen_feats.py

In python2, str and int cannot be concatenated using "+" operator, and
it will cause bugs if dict_id is not assigned. (use auto-incr ids)

vsoch/deepdive,gaapt/deepdive,zifeishan/deepdive,vsoch/deepdive,vasyvas/deepdive,closedLoop/deepdive,maalmeida1837/deepdive,Atlas7/deepdive,wgapl/deepdive,vasyvas/deepdive,AlexisBRENON/deepdive,closedLoop/deepdive,vsoch/deepdive,Gela/deepdive,AlexisBRENON/deepdive,kod3r/deepdive,AlexisBRENON/deepdive,AlexisBRENON/deepdive,RTsWorld/deepdive,gaapt/deepdive,gaapt/deepdive,Gela/deepdive,RTsWorld/deepdive,RTsWorld/deepdive,closedLoop/deepdive,wgapl/deepdive,infinitespace/deepdive,HazyResearch/deepdive,wgapl/deepdive,topojoy/deepdive,HazyResearch/deepdive,topojoy/deepdive,sai16vicky/deepdive,Atlas7/deepdive,nvoron23/deepdive,kod3r/deepdive,nvoron23/deepdive,zifeishan/deepdive,vasyvas/deepdive,nvoron23/deepdive,RTsWorld/deepdive,topojoy/deepdive,sai16vicky/deepdive,Atlas7/deepdive,vasyvas/deepdive,closedLoop/deepdive,Gela/deepdive,Gela/deepdive,kod3r/deepdive,sky-xu/deepdive,HazyResearch/deepdive,infinitespace/deepdive,vasyvas/deepdive,HazyResearch/deepdive,shahin/deepdive,topojoy/deepdive,infinitespace/deepdive,sai16vicky/deepdive,wgapl/deepdive,Atlas7/deepdive,vsoch/deepdive,infinitespace/deepdive,zifeishan/deepdive,maalmeida1837/deepdive,RTsWorld/deepdive,AlexisBRENON/deepdive,wgapl/deepdive,vsoch/deepdive,sai16vicky/deepdive,Atlas7/deepdive,maalmeida1837/deepdive,shahin/deepdive,sky-xu/deepdive,infinitespace/deepdive,zifeishan/deepdive,topojoy/deepdive,sai16vicky/deepdive,nvoron23/deepdive,maalmeida1837/deepdive,closedLoop/deepdive,zifeishan/deepdive,gaapt/deepdive,gaapt/deepdive,maalmeida1837/deepdive,kod3r/deepdive,kod3r/deepdive,nvoron23/deepdive,infinitespace/deepdive,gaapt/deepdive,Gela/deepdive