Update RestSharp dependency

[th0mk]

Because RestSharp has some breaking changes in newer versions this library currently only works if you use version 106.

If you have a higher version of RestSharp in your solution installed the package will return errors.

There are two possible solutions to fix this issue:

• Change package so it always uses the 106 version.
• Update RestSharp to a newer version and fix the code for the new changes

If you update the package a different dependency (from the same author) also has to be updated since it has the same issue: https://github.com/David-Desmaisons/RestSharpHelper