Helpful exception when reading version information with merge conflict

related to https://github.com/CocoaPods/CocoaPods/issues/1853, https://github.com/CocoaPods/CocoaPods/issues/2065, https://github.com/CocoaPods/CocoaPods/issues/2056 etc.
Merge pull request #2067 from segiddins/helpful-exception-on-repo-version-merge-conflict

Helpful exception when reading version information with merge conflict