Added info on troubleshooting Mac installation problems related to the gem native extensions and the Command Line Tools version.
Merge pull request #180 from mjul/master

Mac installation troubleshooting info added.
explicitly convert charseqs
Merge branch 'master' of github.com:calabash/calabash-android
temporary workaround for keytool error

manual run of the keytool command worked fine, so I copied the results
straight into the code.
didn't work, trying different things
Merge remote-tracking branch 'upstream/master'