Change script to allow XCode versions after the required one.

[florenciarosental]

For example, if the required version is 9.0, allow any developer to use any XCode version that came after that, like 9.2

[guidomb]

That would be cool!. Do you feel like submitting a PR with this change? You should add the change here. This script is written in ruby. installed_xcode_version and required_xcode_version are the variables that store the versions to be compared. Currently is just a string comparison. You should probably compare minor and patch versions if mayor version are equal.