Write index.html to provide file navigation

[caufieldjh]

Upon upload to S3 bucket, files should be navigable using simple index.html.
Will need index for all files and for individual OBOs.
Will also need to update upon new uploads (i.e., don't update if no changes).

[justaddcoffee]

Thanks @caufieldjh - expounding on this:

I think we need these index.html's:

s3://s3bucket_name/kg-obo/index.html
^ for this one we need to query the s3 bucket at the end of a run, after everything is written up to s3, to correctly take stock of all new and existing ontology directories

s3://s3bucket_name/kg-obo/[ontology name]/index.html
s3://s3bucket_name/kg-obo/[ontology name]/[version]/index.html
^ for these we can write the index.html inside the for loop where we process a given ontology, after we do the transform

[caufieldjh]

Handled in #25