Warn for deprecated specs on install
[InstallerSpec] Check for deprecation message when spec.deprecated = true
Merge branch 'warn-for-deprecated-specs-on-install' of https://github.com/segiddins/CocoaPods into segiddins-warn-for-deprecated-specs-on-install

* 'warn-for-deprecated-specs-on-install' of https://github.com/segiddins/CocoaPods:
  [InstallerSpec] Check for deprecation message when spec.deprecated = true
  Warn for deprecated specs on install
Merge branch 'segiddins-warn-for-deprecated-specs-on-install'

* segiddins-warn-for-deprecated-specs-on-install:
  [InstallerSpec] Check for deprecation message when spec.deprecated = true
  Warn for deprecated specs on install