Merge pull request #152 from jasvir99/dirty

adds labreport link in index.html and modify form for labreport.
Merge pull request #153 from jasvir99/dirty

adds requirements.txt and updates README.md accordingly.
Update README.md
Taxes and bills are calculated and save in database
Comment added
Merge pull request #156 from aseemmittal/dirty

calculate taxes on purchased order, bill data and save those values in database
Bill rendered properly
Proper information about models included
Merge pull request #157 from aseemmittal/dirty

Bill rendered properly