Add jvmopts

[peterneyens]

I am not sure this completely solves the OOM in our 2.11 travis builds, but there seems to be progress.

[codecov-io]

Codecov Report

Merging #158 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
+ Coverage      80%   80.06%   +0.06%     
==========================================
  Files          33       33              
  Lines         290      291       +1     
  Branches        2        2              
==========================================
+ Hits          232      233       +1     
  Misses         58       58

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