EulerPy 1.2.3 (new formula)

[EulerPy](https://github.com/iKevinY/EulerPy) is a small project I worked on to streamline the process of solving Project Euler problems using Python. I figured it would be nice to allow OS X users install it via Homebrew rather than `pip` so it could be easily updated (when the problem database expands). Prior to working on this formula I had absolutely no experience in Ruby, so I've mostly based this off of the `jrnl` formula.
@mikemcquaid Good point. I assume the relevant piece of code would be `assert_equal 0, $?.exitstatus`, but should this go inside or outside the `Open3.popen()` block? Apologies for my Ruby ignorance.