Update instruction to install mauve-text from source

[jackjyzhang]

Right now the code uses a modified version of mauve to evade their restriction of only allowing gpt2/bert models. Document this in README

[MSheshera]

I've run into this issue! Do you have a fork of https://github.com/krishnap25/mauve with the restriction of gpt2/bert removed?

(Thanks for this work, super helpful!)

[jackjyzhang]

Hi @MSheshera,

Thanks for your patience! The fork with the gpt2/bert restrictions removed is here: https://github.com/jackjyzhang/mauve

Please install from source with this forked repo. We will also update the instruction in README. If you have any additional questions/issues please let us know!

Thanks,
Jack