first commit for clinvitae.py for access to clinvitae REST api

I have prepared a simple first commit for Clinvitae web service (human variant genome database integration)

> Clinvitae().query_gene('gene_name')

Will be the most common query, though it may be useful to build in more methods such as 
> Clinvitae().all_variants('gene_name')
To return a list of all hgvs variants in gene for example.

Please feel free to change or let me know if anything should be changed!