mention BibParser.j alternative (closes #16)

Author: stevengj

README.md

@@ -5,3 +5,7 @@
 [![Docs dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://juliatex.github.io/BibTeX.jl/dev)
 
 Parsing BibTeX files for the Julia language.  Originally based on https://github.com/ptigas/bibpy
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+An alternative package under more active development is:
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+* [BibParser.jl](https://github.com/Humans-of-Julia/BibParser.jl)