Replace FileSystemLoader with PackageLoader
Replace FileSystemLoader with PackageLoader

This is more elegant. We can add FileSystemLoader
later when we allow users to customise their templates
more easily ...
Also removed unused imports

pignacio/python-nvd3,vdloo/python-nvd3,oz123/python-nvd3,yelster/python-nvd3,BibMartin/python-nvd3,Coxious/python-nvd3,pignacio/python-nvd3,mgx2/python-nvd3,pignacio/python-nvd3,yelster/python-nvd3,liang42hao/python-nvd3,yelster/python-nvd3,liang42hao/python-nvd3,liang42hao/python-nvd3,BibMartin/python-nvd3,mgx2/python-nvd3,Coxious/python-nvd3,mgx2/python-nvd3,oz123/python-nvd3,vdloo/python-nvd3,BibMartin/python-nvd3,Coxious/python-nvd3,oz123/python-nvd3,vdloo/python-nvd3