Closes #1815

@orta & @neonichu would be proud!

Merge branch 'issue_1449_duplicate_prefix_header_contents' of https://github.com/luisdelarosa/CocoaPods into luisdelarosa-issue_1449_duplicate_prefix_header_contents

* 'issue_1449_duplicate_prefix_header_contents' of https://github.com/luisdelarosa/CocoaPods:
  Addressed comments from @irrationalfab: - simplified collection of unique prefix_header_contents - reduced sub specs in spec from 4 to 2 Removed inline documentation and added @notes and @todos. Added entry to Changelog.
  Fix issue #1449 by collecting the prefix_header_contents and uniq-ing them.
  Add integration test for issue #1449.
  Added two tests for issue #1449 - however both are passing at the unit level so I suspect that the issue will need to be tested at the integration test level.

Conflicts:
	CHANGELOG.md

[linter] Validate screenshots are valid

Closes #2010

Fix is a bug with nap and has been fixed in nap.

https://github.com/Fingertips/nap/pull/4
Fixes #1998

Added more detailed output to lib create

Use configure file

#760: pod update PODS

Added a functional spec for telling the user that the Pods cannot be updated unless they are installed

e.g. rake 'spec:functional[command/project]'
The single quotes are needed for zsh.

Because it improves the user convenience and bundler does it the same way.

Refactoring: Replaced Installer::Analyzer's getter and setter update_mode by #update, #update= and #update_mode?

Changed signature doc of Pod::Project#run_install_with_update and call it appropriately by Pod::Project::Update#run