fix(tests): fixing wrong derived data path (#92)

Author: milos1290

.slather.yml

@@ -4,6 +4,6 @@ workspace: Example/Leanplum-SDK.xcworkspace
 scheme: Leanplum-SDK-Example
 source_directory: Leanplum-SDK/
 output_directory: coverage-report
-binary_file: /DerivedData/Build/Products/Debug-iphonesimulator/Leanplum-SDK_Example.app/PlugIns/Leanplum-SDK_Tests.xctest/Frameworks/Leanplum.framework/Leanplum
+binary_file: DerivedData/Build/Products/Debug-iphonesimulator/Leanplum-SDK_Example.app/PlugIns/Leanplum-SDK_Tests.xctest/Frameworks/Leanplum.framework/Leanplum
 ignore:
   - Leanplum-SDK/Classes/Vendor/**