Don't encode XML entities in project paths for workspaces.

Get the raw value of the location attribute instead of using to_s, which encodes entities. This fixes issues when an Xcode project path contains characters that would otherwise be encoded as an XML entity such as an apostrophe ('). While it is likely more "correct" to encode these entities, Xcode doesn't do it nor does it decode them.

The problem is demonstrated if you use Cocoapods with an Xcode project with an apostrophe ( ' ) character in its path. After pod update, the workspace will contain an additional, broken project with the apostrophe replaced by &apos;.