eigen link broken in readme

[mfe7]

thanks for this great repo. i'm just getting started with it, but so far i see that the link to eigen was broken (moved to gitlab). the following two lines in the readme could be updated to reflect this change:

• change wget -O eigen.zip http://bitbucket.org/eigen/eigen/get/3.3.7.zip to wget -O eigen.zip https://gitlab.com/libeigen/eigen/-/archive/3.3.7/eigen-3.3.7.zip
• unzip eigen.zip -d eigen-3.3.7 to unzip eigen.zip

[arjunskumar]

Thanks @mfe7 . Updated the readme.