Add missing require in my-packages.el

my-packages.el was causing errors on load due to a function not being
defined.  This change adds the needed require.
Add paredit hooks, OS specific conf, Markdown mode

Enable paredit mode for certain major modes via mode hooks.

Add OS specific config.  Conditionally load OS specific config
libraries. Detect OS using system-type variable.

Markdown mode package added.
Add windows specific config

Currently all we need to do for Windows is set the default font.
Update README to be more descriptive