Add a README.md file

The README.md contains the instructions to install Odyssey as a Vim
plugins. The other sections may not have that much importance (simple
introduction and license section).

README.md

@@ -0,0 +1,39 @@
+# Odyssey for Vim
+
+Odyssey is a dark green colorscheme for Vim.
+
+## Installation
+
+### Downloading the plugin
+
+#### Using `./vim/colors/`
+
+Copy the file `./vim-odyssey/colors/odyssey.vim` under the repertory
+`./vim/colors`.
+  ```zsh
+  git clone https://github.com/ludokng/vim-odyssey.git vim-odyssey/
+  cp vim-odyssey/colors/odyssey.vim ~/.vim/colors/
+  ```
+
+#### Using [pathogen.vim]
+
+After having installed [pathogen.vim], clone the repository under
+`./vim/bundle`.
+  ```zsh
+  cd ~/.vim/bundle/
+  git clone https://github.com/ludokng/vim-odyssey.git vim-odyssey/
+  ```
+
+### Updating the `./vimrc`
+
+Add the following to the `./vimrc` file.
+  ```vim
+  set termguicolor
+  colorscheme odyssey
+  ```
+
+## License
+
+Odyssey for Vim is distributed under the terms of the MIT license.
+
+[pathogen.vim]:  https://github.com/tpope/vim-pathogen