Edi-835-parser

A minor update with the following changes:

- Added support for `.DAT` files
- Added tracking of claim `ICNs`
- Added tracking of "claim forwarding" wherein payers state if the claim was forwarded to another payer (e.g. a secondary or tertiary).

Added the ability to parse claim status codes. Doing this allowed for the addition of a `payer_classification` column to the output of `transaction_sets`.`to_dataframe` method. The `payer_classification` column explicitly states if the given transaction, at the service level, is from a primary payer, secondary payer, or tertiary payer. In the case of denials the `payer_classification` is given as `unspecified`, if the claim status code went unparsed, the `payer_classification` is given as `unknown`.

This release includes a few extra parsing checks. This parser now accepts `.835` files and correctly parses the `<` delimiter. Tests were added to ensure correct delimiter identification. A `payee` property was also added to the transaction set for easier payee identification.

Behind the scenes, this update also includes continuous integration testing for any commit pushed to source code on GitHub for increased stability.

This release contains a fix to a bug in the amount segment attribute of the claim loop and added service allowed amounts (where available) to the `to_dataframe` method for better accounting.

This update includes a lot of small updates to the parser to make it more succinct and accurate. Changes include teasing out allowed unit values from billed unit values, generalization of claim indices to include strings, the inclusion of more service segment values, standardization of adjustments, remarks, and references and better code, description modeling.

Added a special acknowledgment to the README.

Fixed some assumptions that were being made about the adjustments, remarks, and references attached to the individual services within each claim. Dataframe functionality extended to display every adjustment, remark and reference of each service.