change dylibs staging directory and stabilize CI

Companion to PR https://github.com/calabash/calabash-ios/pull/478

#### Stage dylibs in calabash-dylibs

We have been staging in calabash.dylibs.  I sat on this change for a few days and decided it was clearer not to stage to a .dylibs directory; there is no MacOS .dylibs directory naming convention (like .framework).

#### Fix CI

Nightly CI against the master toolchain has been failing because the calabash-ios gem build_server rake task could not build the dylibs. FIXED PR 478

Travis CI has been failing because the calabash-ios gem requires run_loop >= 1.0.0.pre4 which has not been released.