upgraded node version for travis
upgraded node version for travis

pfarnach/pdfmake,mubassirhayat/pdfmake,mweslander/pdfmake,Novlr/pdfmake,compact/pdfmake,compact/pdfmake,mdoelker/pdfmake,Intia/pdfmake,Intia/pdfmake,atsuyim/pdfmake,tanem/pdfmake,jodeng110/udpcloud-pdfmake,dennisrjohn/pdfmake,wbswbs/pdfmake,jiusanzhou/pdfmake,mdoelker/pdfmake,Nishi-Inc/pdfmake,bavellone/pdfmake,mweslander/pdfmake,TW-QEN/pdfmake,naoa/pdfmake,mubassirhayat/pdfmake,TW-QEN/pdfmake,ILUMY/pdfmake,jiusanzhou/pdfmake,jodeng110/udpcloud-pdfmake,naoa/pdfmake,wbswbs/pdfmake,Nishi-Inc/pdfmake,tanem/pdfmake,atsuyim/pdfmake,Novlr/pdfmake,ILUMY/pdfmake,dennisrjohn/pdfmake,pfarnach/pdfmake,bavellone/pdfmake