fixed build by adding -destination to iOS unit test command in .travis.yml

.travis.yml

@@ -8,7 +8,7 @@ before_install:
 
 script:
   - set -o pipefail
-  - xcodebuild -workspace 'Masonry.xcworkspace' -scheme 'Masonry iOS Tests' -configuration Debug -sdk iphonesimulator clean test ARCHS=i386 VALID_ARCHS=i386 ONLY_ACTIVE_ARCH=NO GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -c
+  - xcodebuild -workspace 'Masonry.xcworkspace' -scheme 'Masonry iOS Tests' -configuration Debug -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone 7,OS=10.0' clean test ARCHS=i386 VALID_ARCHS=i386 ONLY_ACTIVE_ARCH=NO GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -c
   - xcodebuild -workspace 'Masonry.xcworkspace' -scheme 'Masonry iOS' -configuration Debug -sdk iphonesimulator clean build ARCHS=i386 VALID_ARCHS=i386 ONLY_ACTIVE_ARCH=NO | xcpretty -c
   - xcodebuild -workspace 'Masonry.xcworkspace' -scheme 'Masonry OSX' -configuration Debug clean build | xcpretty -c