fix legend sorting when attributes have items of type different from string_types
fix legend sorting when attributes have items of type different from string_types

schoolie/bokeh,dennisobrien/bokeh,justacec/bokeh,philippjfr/bokeh,aiguofer/bokeh,timsnyder/bokeh,philippjfr/bokeh,rs2/bokeh,Karel-van-de-Plassche/bokeh,phobson/bokeh,percyfal/bokeh,Karel-van-de-Plassche/bokeh,ericmjl/bokeh,dennisobrien/bokeh,stonebig/bokeh,jakirkham/bokeh,percyfal/bokeh,stonebig/bokeh,jakirkham/bokeh,bokeh/bokeh,DuCorey/bokeh,DuCorey/bokeh,mindriot101/bokeh,mindriot101/bokeh,schoolie/bokeh,timsnyder/bokeh,phobson/bokeh,percyfal/bokeh,Karel-van-de-Plassche/bokeh,percyfal/bokeh,timsnyder/bokeh,ptitjano/bokeh,rs2/bokeh,ericmjl/bokeh,rs2/bokeh,phobson/bokeh,draperjames/bokeh,philippjfr/bokeh,aiguofer/bokeh,quasiben/bokeh,rs2/bokeh,schoolie/bokeh,ericmjl/bokeh,dennisobrien/bokeh,ericmjl/bokeh,azjps/bokeh,Karel-van-de-Plassche/bokeh,DuCorey/bokeh,rs2/bokeh,aiguofer/bokeh,clairetang6/bokeh,mindriot101/bokeh,schoolie/bokeh,ptitjano/bokeh,bokeh/bokeh,ptitjano/bokeh,philippjfr/bokeh,jakirkham/bokeh,clairetang6/bokeh,bokeh/bokeh,phobson/bokeh,clairetang6/bokeh,justacec/bokeh,stonebig/bokeh,draperjames/bokeh,azjps/bokeh,aiguofer/bokeh,aiguofer/bokeh,timsnyder/bokeh,quasiben/bokeh,dennisobrien/bokeh,draperjames/bokeh,jakirkham/bokeh,azjps/bokeh,bokeh/bokeh,jakirkham/bokeh,philippjfr/bokeh,Karel-van-de-Plassche/bokeh,DuCorey/bokeh,azjps/bokeh,aavanian/bokeh,quasiben/bokeh,draperjames/bokeh,stonebig/bokeh,ptitjano/bokeh,percyfal/bokeh,dennisobrien/bokeh,justacec/bokeh,aavanian/bokeh,timsnyder/bokeh,mindriot101/bokeh,aavanian/bokeh,bokeh/bokeh,ptitjano/bokeh,draperjames/bokeh,ericmjl/bokeh,schoolie/bokeh,clairetang6/bokeh,justacec/bokeh,azjps/bokeh,DuCorey/bokeh,aavanian/bokeh,aavanian/bokeh,phobson/bokeh