ADD: Two level sort function

This commit add the first interesting difference from freitass original
version. It provides a two level sort function which allow the user to sort
the todo by project (or context) then by priority.

TODO: Maybe think about three level sort (project, context, priority) in any
order.

README.markdown

@@ -1,9 +1,24 @@
+# Readme
+
+## What is this plugin ?
+
+This plugin is a fork of freitass todo.txt (see section 1.3) vim plugin adding
+a nice two level sorting function designed for todo.txt files (see section
+1.4).
+
+## Install
+
 ### Quick install
 
-    git clone git://github.com/freitass/todo.txt-vim.git
+    git clone git://github.com/dbeniamine/todo.txt-vim.git
     cd todo.txt-vim
     cp -R * ~/.vim
 
+### Pathogen install
+
+    git clone git://github.com/dbeniamine/todo.txt-vim.git ~/.vim/bundle/todo.txt-vim
+
+## Features included in Freitass version
 
 This plugin gives syntax highlighting to [todo.txt](http://todotxt.com/) files. It also defines a few
 mappings, to help with edition of these files:
@@ -22,3 +37,21 @@ mappings, to help with edition of these files:
 
 If you want the help installed run ":helptags ~/.vim/doc" inside vim after having copied the files.
 Then you will be able to get the commands help with: :h todo.txt
+
+## New features
+
+This fork provides a two level sorting function designed to do by project or
+by context sorts, with a priority sort.
+
+`<leader>-sc` : Sort the file by context (reverse) then by priority
+`<leader>-sp` : Sort the file by project (reverse) then by priority
+
+The user can give argument for the two call to vim sort function by changing
+the following variables in its vimrc:
+see :help sort
+    let g:Todo_txt_first_level_sort_mode="! i"
+    let g:Todo_txt_second_level_sort_mode="i"
+
+## Todo
+
+Complete documentation