Complete rewrite of the back end using bibtexparser and jinja2.

Signed-off-by: Chamon <[luizchamon] [gmail]>
Include a local copy of bibtexparser 0.6.0 for completeness (only necessary if you didn't get it from PyPi).

Signed-off-by: Chamon <[luizchamon] [gmail]>
- auxfun brings some Jinja filters and customizations for BibTexParser.
- Styles includes an IEEE-like definition and a blank default style.

Signed-off-by: Chamon <[luizchamon] [gmail]>
Update README and fix small issues.