Fix tree decoration based on file status on Windows
Fix tree decoration based on file status on Windows

Two parts
 1. The local path returned by transformClientPathToLocalPath had a mix of separators (clientRoot used Windows "\" and match[1]
    has posix ("/"). Changing to use path.join "does the right thing".
 2. The data-path attribute of tree nodes uses the platform separators.
    The problem is that backslashes need to be escaped in the call to
    querySelectorsAll - new function escapeBackSlashes does this.

mattsawyer77/atom-perforce,unional/atom-perforce