Adding a comment in case one wants to ignore .xcworkspace

[Fastlane] Specify screenshot files only, rather than whole folder (in case the user has frameit config)

The whole screenshots folder shouldn't be ignore since there could be frameit configuration in it (Framefile.json, fonts, background.jpg, *.strings, etc...). It'd be better to just ignore the generated PNG screenshot files.

The Objective-C and Swift gitignore files are missing `*.xccheckout`
and `*.xcscmblueprint`, but these are still included in the Xcode
gitignore. This commit synchronises the three files.

The files themselves contain information about the user's local
source control status and shouldn't be included in most Xcode
repositories.

`*.xcuserstate` appears to always be contained in `xcuserdata/`
which is already ignored.

After trying this tool for code injeciton: https://github.com/johnno1962/injectionforxcode we added it to our workflow.
Only bad side is that there's a folder included in the project that would be worth ignoring.
We had it in our .gitignore file. Just pushing the change

Fastlane now has a mono repo, the documentation moved into the folder fastlane/docs

These files are automatically generated by Xcode and maintain
information regarding source control. Xcode is typically used
in Objective-C and Swift projects, so add these to the ignored files for
these platforms.

some details based on #1221

This updates the link provided to the CocoaPods documentation regarding whether the Pods directory should be ignored or not.

removing this aditional white space avoid a mistake for beginners developers ignore the pod directory, because is confusing to note when they remove the '#' character and git still is tracking the pod dir.

This got changed recently.

xcuserstate files are generated from within Xcode and saved in your project bundle to remember your last opened file, the open state of any group folders, open tabs, and any other user setting your project might need to remember

We shouldn't be ignoring these, it's down to the user and we shouldn't enforce them to ignore the `Pods/` directory

http://guides.cocoapods.org/using/using-cocoapods.html#should-i-ignore-the-pods-directory-in-source-control?

The pattern `*.xccheckout` is already ignored on line 15.

This is a file that Xcode 5 uses for version control, doesn't need to be checked in. Also see http://stackoverflow.com/a/18448100/1877078

Per discussion in #148.