Don't test 1.8.7 on Travis
Don't test 1.8.7 on Travis

Works locallu sing 32 and 64 bit 1.8.7-p370 and ree-1.8.7-2012.02,
just breaks on Travis, like:

http://travis-ci.org/#!/sj26/zipstream/jobs/2115312

  1) Zipstream::Body should stream as a body
     Failure/Error: zip.write "README", "This is a README!"
     RangeError:
       bignum too big to convert into `unsigned long'
     # ./lib/zipstream.rb:38:in `pack'

sj26/zipstream