provide a test script for travis to test mpi

[coveralls]

Pull Request Test Coverage Report for Build 747

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 27 unchanged lines in 8 files lost coverage.
• Overall coverage decreased (-0.2%) to 91.826%

---

Files with Coverage Reduction	New Missed Lines	%
spotpy/database/sql.py	1	94.0%
spotpy/algorithms/_algorithm.py	2	86.64%
spotpy/database/csv.py	2	90.0%
spotpy/algorithms/sceua.py	2	89.19%
spotpy/describe.py	4	85.87%
spotpy/parameter.py	5	93.97%
spotpy/algorithms/demcz.py	5	91.8%
spotpy/algorithms/dream.py	6	89.22%
<!--	Total:	27		-->

Totals
Change from base Build 743:	-0.2%
Covered Lines:	5437
Relevant Lines:	5921

---

💛 - Coveralls