add RucioDocsParser and IssueParser

[mageirakos]

Motivation

Now that the fetching of the Issues and Documentation data is complete #8.
We need to create the appropriate classes that will handle any processing/metadata creation etc that the bot is going to need.

Modification

1. Expand our parsing module to handle the new input data sources
2. Create the scipts that utilize the new classes/methods

[mageirakos]

To correctly integrate this I'm going to have to change how the EmailParser works as well. A factory method will once again be used in this case to make it easier to understand the flow of the data. Also, so that we don't deprecate the dataset_creation.py script after fixing this issue we'll keep the eparser.py code as is for now and create a new file for our these updated parsers.