Added an "installer" ( see issue #56 )

[joseywoermann]

This pull request adds a setup.bat file, which sets up everything required to self-host MisteriBot (see #56).

It asks the user for the token and saves that to a file, creates a virtual environment, installs the required packages and starts the bot. This reduces the hassle of starting / setting up the bot significantly.

What this means for you as a developer:

• Relative paths have changed slightly: Instead of ../data/usr/prefix.json you now have to use bot/data/usr/prefix.json, because the entry point (setup.bat) now lies in the root of your project.
• Whenever you install a new package, add its name to requirements.txt, so that the setup script installs them automatically.
• You now use a virtual environment. Packages are now installed separately instead of cluttering up your PC.

Other than that, I have tweaked the code slightly.

[therealmistericraft]

OMG, thank you!

[EinfachRuwen]

Amazing