Improve wording for ctrlp_working_path_mode

Fixes #397

Author: Angelo Olivera

doc/ctrlp.txt

@@ -181,13 +181,12 @@ variable: >
   let g:ctrlp_working_path_mode = 'ra'
 <
   c - the directory of the current file.
-  a - like "c", but only applies when the current working directory outside of
-      CtrlP isn't a direct ancestor of the directory of the current file.
-  r - the nearest ancestor that contains one of these directories or files:
+  a - the directory of the current file, unless it is a subdirectory of the cwd
+  r - the nearest ancestor of the current file that contains one of these
+      directories or files:
       .git .hg .svn .bzr _darcs
-  w - begin finding a root from the current working directory outside of CtrlP
-      instead of from the directory of the current file (default). Only applies
-      when "r" is also present.
+  w - modifier to "r": start search from the cwd instead of the current file's
+      directory
   0 or <empty> - disable this feature.
 
 Note #1: if "a" or "c" is included with "r", use the behavior of "a" or "c" (as

readme.md

@@ -51,8 +51,9 @@ Use `:diffthis` when opening multiple files to run `:diffthis` on the first 4 fi
     ```
 
     `'c'` - the directory of the current file.  
-    `'r'` - the nearest ancestor that contains one of these directories or files: `.git` `.hg` `.svn` `.bzr` `_darcs`  
-    `'a'` - like c, but only if the current working directory outside of CtrlP is not a direct ancestor of the directory of the current file.  
+    `'a'` - the directory of the current file, unless it is a subdirectory of the cwd  
+    `'r'` - the nearest ancestor of the current file that contains one of these directories or files: `.git` `.hg` `.svn` `.bzr` `_darcs`  
+    `'w'` - modifier to "r": start search from the cwd instead of the current file's directory  
     `0` or `''` (empty string) - disable this feature.
 
     Define additional root markers with the `g:ctrlp_root_markers` option.