Build JVM before JS on travis

[peterneyens]

If there are no other builds (for other PRs, branches, ...), switching the JVM/JS order to JS/JVM can be 10-15 minutes quicker.

There are now 6 Travis jobs for every build (3 Scala versions and JVM / JS) and only 5 are executing at the same time. By switching the order, the three longer JVM jobs are started first and when the 2.11 JS job finishes, the 2.12 JS job can start (which doesn't take as long as the 2.12 JVM job which is now started last).

I ran Travis twice resulting in total build times of 31 and 39 minutes while the last master builds took around 50 minutes.

This is just a minor improvement of the Travis matrix build change by @kailuowang in #1671.

[codecov-io]

Codecov Report

Merging #1691 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1691   +/-   ##
=======================================
  Coverage   93.94%   93.94%           
=======================================
  Files         241      241           
  Lines        4096     4096           
  Branches      156      156           
=======================================
  Hits         3848     3848           
  Misses        248      248

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[kailuowang]

This is great. Thanks! I plan to research how to have more than 5 concurrent executions, but I guess you already did and it's not possible.

[djspiewak]

This is great. Thanks! I plan to research how to have more than 5 concurrent executions, but I guess you already did and it's not possible.

It's part of their commercial offering.