deps: use bn.js
0.4.0
rfc3280: 0.4.0
rfc2560: 0.4.0
Properly encode IMPLICIT tag
Fix both explicit and implicit tags for submodel
rfc-3280: fix Certificate encoding
rfc3280: 0.4.1
Add choice tests
Plug submodels with function call.

Implemented as suggested in #14
Fix encoding of CHOICE
Fix code style (less spaces)
Make naming more consistent and obey codestyle