Fix source URL for Main.storyboard in recipe
Fix source URL for Main.storyboard in recipe

In the recipe, the command to install an example `Main.storyboard`
uses shell escaping:

> `curl '`…`/iOS\ Example/Source/Base.lproj/Main.storyboard' -o Source/Base.lproj/Main.storyboard`

which results in a 404 error.

With shell escaping replaced by proper URL encoding, the URL works:

> `curl '`…`/iOS%20Example/Source/Base.lproj/Main.storyboard' -o Source/Base.lproj/Main.storyboard`

fulldecent/swift3-module-template,fulldecent/swift3-module-template