prep for 0.18.4 (jump-dev#1530)

tidy REQUIRE

prep v0.18.2 (jump-dev#1334)

Prep for v0.18.1

prep for 0.18.0

prep for 0.17.1

Add Julia v0.6 on Travis

Merge pull request jump-dev#1002 from JuliaOpt/mlubin-patch-1

update bound on ForwardDiff

prep for 0.16.1

Merge pull request jump-dev#979 from JuliaOpt/ml/tidy

fix ip_dual_solvers and relaxation test