Use parsebib.el
Fix doc string of helm-bibtex-prep-entry
Merge pull request #22 from joostkremers/parsebib

Now using Joost Kremer's parsebib package for parsing bibtex files.
List newest entries at the top as before.

Parsebib returns the entries in the order in which they occur in the bib file.
README.md: Update dependencies.
Updated package dependencies.