Gene conversion fixes

[katehoffshutta]

This PR includes several changes:

1. In gene mapping, switch subset to left_join to preserve ordering of input list
2. Change unit tests so that ordering of test input does not match ordering of gene_mapping, to confirm order preservation of input list
3. Changed how we handle ensembl mapping to return columns of ensembl IDs with and without version (the version parameter is now include_no_version and is set to TRUE by default)
4. Added an exception for the case where a user inputs ensembl IDs that are a mix of versioned and unversioned (we can figure out how to support this later if it is a use case we see people having)
5. Added function names to stop and stdout messages