test against tagged DiffBase versions instead of DiffBase master

Author: jrevels

.travis.yml

@@ -13,7 +13,7 @@ script:
         julia -e 'Pkg.clone(pwd()); Pkg.build("ForwardDiff"); Pkg.checkout("DiffBase"); Pkg.test("ForwardDiff"; coverage=true)';
         julia -O3 -e 'include(joinpath(Pkg.dir("ForwardDiff"), "test/SIMDTest.jl"))';
       else
-        julia -e 'Pkg.clone(pwd()); Pkg.build("ForwardDiff"); Pkg.checkout("DiffBase"); Pkg.test("ForwardDiff"; coverage=true)';
+        julia -e 'Pkg.clone(pwd()); Pkg.build("ForwardDiff"); Pkg.test("ForwardDiff"; coverage=true)';
       fi
 after_success:
     - julia -e 'cd(Pkg.dir("ForwardDiff")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())'