Fix spelling mistake and clean up blank lines
Add header partial to theme

Header partial completes up to step 2 of "writing partial template
files". It wil display the logo, blog title and blog description.
Add call to header partial
Add notes about partials in files
Add footer partial to theme

Footer partial contains rss link, copyright message and attribution to
Ghost. Finishes up to step 9 of the "writing partial template files"
secion.