Add config file

[jankrepl]

One could control things that are not controllable via CLI:

• colors

[AbhayAysola]

• Custom path for sample and ls could also be taken from config

[jankrepl]

• Custom path for sample and ls could also be taken from config

Very much related to #58.

@AbhayAysola I wonder what would be your usecase? I would imagine it is flexibility. The idea behind putting everything in ~/.mltype is to be able to run mlt ls and mlt sample from anywhere.

[AbhayAysola]

That way, I could seperate models by folder to organise them well. Like Python related models in a Python folder, General English related go in English folder etc. When I want to use other models, I would just switch the path. The config file also wouldn't have to be manually updated, a command like mlt config could also work.

[AbhayAysola]

• default number of chars to generate
• set key combination to exit

[jankrepl]

The config file logic was added in #89.
One can easily set defaults to all options for any of the commands of the CLI (e.g. number of characters)

Additionally, define any parameters inside of the general section then can be read anywhere within the code
mltype.utils.get_config_file. So there can be new pull requests using this logic.