[DOC] convertFA2Tree

[the-mayer]

MolEvolvR contains functions with very similar/duplicate functionality:

Previous Name	Current Name
convert_fa2tre	convertFA2Tree
generate_fa2tre	convertFA2Tree

These functions should be disambiguated, or refactored so that they can be combined with a parameter switching between the different functionality.

Originally posted by @teddyCodex in #54 (comment)

[Klangina]

I'd like to work on this, may I be assigned this issue?

[jananiravi]

sure, go for it!