see #27 and #28

Option to select style from bibliography tab

Added an option (-s/--style) to allow to select
the style in every invocation of the bibliography
tag individually.

see #26

see #26

fixes #17

see #16

#19

Proper fix for issue #16

In essence we withold application of the :latex filter until we
do html generation.

update dependencies

#14

#14

document tag parameters

Normalize tag parameters using Ruby's OptionParser. This
breaks the API but gives us a standard way of handling
parameters going forward.

This commit also adds optional prefixes used by the
bibliography, cite and reference tags. See #12.