Shellfire

Minor bug fixes.
Adds Marker indices to the marker config output.

This is a major change to how the interface works. Based on user feedback, we now have two separate modes of operation:

* config mode _(used for configuring how payloads are processed.)_
* shell mode _(used for sending payloads.)_

There's also a basic fuzzing feature now (still WIP.)

This version comes with a bunch of updates:
* _shellfire_ now supports Python Requests Sessions. Cookies are dynamically updated, and custom cookies are overlaid on top.
* a re-branded banner! (such amaze. much leet.)
* new --version flag.
* support for parsing url encoded params for cookies, headers, and post data.
* tons of bug fixes.

Now, we can specify `.method form` for multipart form data, and we can specify files to upload with it. There are two ways we can do this:

* specify `filename` to upload a raw file.
* specify the name of a plugin to use to generate the file upload content.

There was an error importing the new plugin system if your ~/.config/shellfire/plugins path didn't exist yet. This should now be resolved.

Lot's of changes, including...
* a new plugin system!
* new flexibility for output markers and splitting.
* injection support for POST, cookies, and headers.
* properly packaged for distribution 😉
* and more!