exclude swiftmodule from Product search

[lampietti]

Sometimes, Slather returns "No product binary found" while there's one in the build dir...
After a debug session it appears that the "first" found_product is the .swiftmodule and not the .app.
Excluding it like the .dSYM get it working again !

Closes #347

[coveralls]

Coverage increased (+0.002%) to 95.437% when pulling 66f41c6 on lampietti:exclude_swiftmodule into 15845e6 on SlatherOrg:master.

[ksuther]

Thanks!