Reduced test run time

I've reduced the time limit for the jmh tests. They can still take up to 3s each, I think-- still not great for a unit test, but I found the run times much more palatable than before (as in, the test suite runs through in less than two minutes on the machine that I tried). Feel free to merge and/or adapt.

I also added a parameter for setting collection size, since I thought that might be related, but ended up not using that; feel free to adapt.