Property test failure for DecayedVector associativity law

[Gabriella439]

The travis run for #504 failed due to this unrelated property test failure. I wanted to document this test failure before re-running the build:

DecayedVectorProperties:
- DecayedVector[Map[Int, _]] is a monoid *** FAILED ***
  GeneratorDrivenPropertyCheckFailedException was thrown during property evaluation.
   (CheckProperties.scala:12)
    Falsified after 97 successful property evaluations.
    Location: (CheckProperties.scala:12)
    Occurred when passed generated values (
      arg0 = DecayedVector(Map(0 -> 1.092551019411429E-131, -2147483648 -> -5.1395923349246496E-186, 1123520091 -> -1.054823144609479E81, 1729172390 -> 2.7044208603297777E-204, -1025632385 -> -2.6407550299049166E83, -1531213747 -> 9.369914461173615E-108, 2147483647 -> 6.626359682722528E214, -1 -> 9.183701042114227E-121, 1733000002 -> 1.9054796907962035E-69, 1486261998 -> -3.596548607681309E298),163.61309015320558),
      arg1 = DecayedVector(Map(-598566802 -> 6.577216091443459E139, 0 -> -6.983106581761733E-277, -2147483648 -> 2.342555746417487E-40, 632527220 -> -2.3333295474907424E298, 1324313138 -> -1.3316688267759788E43, 1 -> 4.1451020160374474E299, -1910791798 -> -5.435946942714159E-121, -1527223724 -> -9.872547430511853E-76, 281715171 -> 1.8704338950023695E230, -1750186269 -> -5.20859154969638E134, -1954287450 -> -1.351162722951793E152, -361212262 -> -4.2252458754613075E-10, -1750371575 -> 1.0376778496030217E44, -933248926 -> -1.1693913691150838E217, 2062788673 -> 1.0096883954466186E-290, 1478204358 -> -1.2452272296698936E272, -165014830 -> 5.944188692867305E-287, 2147483647 -> 3.642806111063625E-158, -1 -> 2.811285012443069E-275, -1398584131 -> -1.0153759449349607E-141, -157620687 -> 7.230902394992512E-16, -929693903 -> -3.0295675044935256E-227, -1114525533 -> -7.819234650093265E281, -1896996985 -> 3.769131175409155E238, 283045390 -> 1.5774609977149385E-208, 1277853178 -> 2.3371887462781075E-284, -457465990 -> -1.032428206270134E136, 1201651808 -> 1.3609818623724693E-248, -1299781942 -> 2.1053604835146857E-226),98.83099596769675),
      arg2 = DecayedVector(Map(0 -> 5.069061949312889E-129, -2147483648 -> -1.9888890321535495E-134, -1017379625 -> -6.16266401335239E-238, 836614784 -> -4.465702393092752E-238, 688855394 -> 1.2632151678455808E-104, 1 -> 1.3222284050444336E-250, -2006129014 -> -1.6216239905732755E-224, 1769947823 -> -3.6186964077626413E-59, 1442918758 -> 2.3505102506937567E297, 307607698 -> 2.6718064060040822E-101, 1329464480 -> 7.104677292368841E-303, 107123559 -> -4.448181519800882E304, 340663295 -> -4.7496522626173196E-9, -2132606384 -> 4.8953396272111E-83, 93030435 -> 9.747251529309707E238, -2050513270 -> -2.6092689928548686E-215, 1458010495 -> 4.1776257291824907E21, -1159846307 -> -2.6689906955553746E-8, -2072249033 -> 9.277547143042739E170, 1567274304 -> -1.0312004392064934E-25, 2147483647 -> 1.700193640404291E-124, -1 -> -1.1757700786168898E114, 667476306 -> -1.668134135203867E-144, -1092007837 -> 5.902337180686639E274, 792383070 -> 6.430758090909138E-99, -779966986 -> 6.952321859136565E-203, -1350719515 -> 3.7903284081586652E233, -991327069 -> -3.6020329962916166E-5, -1870446096 -> -1.5270123749662104E207, 606237506 -> 1.7479813502207683E-175, -1251275320 -> -3.469186495596741E-43),163.36335413829218)
    )
    Label of failing property:
      isAssociativeEq

[johnynek]

doubles are not associative, so I guess we just need to loosen the bounds here or use doubles in a tighter range.