More autoload documentation.

As discovered through discussions at composer/composer#763

Resubmitted after travis complained, lets try again.

doc/04-schema.md

@@ -349,7 +349,10 @@ since it offers greater flexibility (no need to regenerate the autoloader when y
 classes).
 
 Under the `psr-0` key you define a mapping from namespaces to paths, relative to the
-package root. Note that this also supports the PEAR-style convention.
+package root. Note that this also supports the PEAR-style non-namespaced convention.
+
+The PSR-0 references are all combined, during install/update, into a single key => value 
+array which may be found in the generated file `vendor/composer/autoload_namespaces.php`.
 
 Example:
 
@@ -372,6 +375,17 @@ you can specify them as an array as such:
         }
     }
 
+The PSR-0 style is not limited to namespace declarations only but may be 
+specified right down to the class level. This can be useful for libraries with 
+only one class in the global namespace. If the php source file is also located 
+in the root of the package, for example, it may be declared like this:
+
+    }
+        "autoload": {
+            "psr-0": { "UniqueGlobalClass": "" }
+        }
+    }
+
 If you want to have a fallback directory where any namespace can be, you can
 use an empty prefix like:
 
@@ -381,6 +395,14 @@ use an empty prefix like:
         }
     }
 
+***Note: This will have an impact on performance and also keep in minh that this 
+method forfeits it's uniqueness and there is nothing preventing another "" entry,
+from another packoge perhaps, taking its place. Use with caution.***
+
+The `classmap` references are all combined, during install/update, into a single 
+key => value array which may be found in the generated file 
+`vendor/composer/autoload_classmap.php`.
+
 You can use the classmap generation support to define autoloading for all libraries
 that do not follow PSR-0. To configure this you specify all directories or files
 to search for classes.