Adding Pioneer journal paper to reference list

[michaelcdevin]

Resolves #370

[coveralls]

Pull Request Test Coverage Report for Build 11295368056

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.07%) to 94.514%

---

Files with Coverage Reduction	New Missed Lines	%
wecopttool/core.py	2	92.68%

Totals
Change from base Build 11281900098:	-0.07%
Covered Lines:	2774
Relevant Lines:	2935

---

💛 - Coveralls

[michaelcdevin]

@ryancoe FYI checking this locally should now work with #374 being merged into dev.

Beyond that, this unintentionally opened up a can of worms a bit... There was a typo I missed in that PR, so I made #375 to resolve it, but that is now mysteriously failing for a completely unrelated error in Tutorial 4 which somehow never showed up in the CI until now. I will make a new issue for both the Tutorial 4 bug and the inconsistent CI testing if it makes sense to do so.

Ultimately though, the CI documentation build is broken anyway until #366 is fixed, so this specific PR can be merged whenever you check your local build and approve this PR.