makefile: added doc target
makefile: added doc target

This target is used to generate docs in html format.

Closes #104.

Endika/tsuru,hcxiong/tsuru,hugoantunes/tsuru,Endika/tsuru,hugoantunes/tsuru,mderaldo/tsuru,cgvarela/tsuru,kgrvamsi/tsuru,ggarnier/tsuru,guilhermebr/tsuru,ggarnier/tsuru,RichardKnop/tsuru,gwmoura/tsuru,cezarsa/tsuru,guilhermebr/tsuru,RichardKnop/tsuru,4eek/tsuru,4eek/tsuru,tsuru/tsuru,guilhermebr/tsuru,Endika/tsuru,ArxdSilva/tsuru,ArxdSilva/tsuru,RichardKnop/tsuru,guilhermebr/tsuru,tsuru/tsuru,ArxdSilva/tsuru,tuxmonteiro/tsuru,tsuru/tsuru,cgvarela/tsuru,firebitsbr/tsuru,cezarsa/tsuru,cezarsa/tsuru,cgvarela/tsuru,firebitsbr/tsuru,jblancett/tsuru,ggarnier/tsuru,kgrvamsi/tsuru,jblancett/tsuru,cezarsa/tsuru,gciotta/tsuru,tuxmonteiro/tsuru,firebitsbr/tsuru,4eek/tsuru,gwmoura/tsuru,hcxiong/tsuru,tuxmonteiro/tsuru,mderaldo/tsuru,ggarnier/tsuru,gciotta/tsuru,mderaldo/tsuru,tsuru/tsuru,hcxiong/tsuru,gciotta/tsuru,kgrvamsi/tsuru,gwmoura/tsuru,jblancett/tsuru,ArxdSilva/tsuru