Updated the readme with a note about performance and disabling file s…

…tatus on an individual repo basis.

readme.md

@@ -16,6 +16,8 @@ Usage
 See `profile.example.ps1` as to how you can integrate the tab completion and/or git prompt into your own profile.
 Prompt formatting, among other things, can be customized using `$GitPromptSettings`, `$GitTabSettings` and `$TortoiseGitSettings`.
 
+Note on performance: displaying file status in the git prompt for a very large repo can be prohibitively slow. Rather than turn off file status entirely, you can disable it on a repo-by-repo basis by adding individual repository paths to $GitPromptSettings.RepositoriesInWhichToDisableFileStatus.
+
 Installing
 ----------