Added a brandmark / logo and adjusted css

[mbsouth]

modified:
public/css/main.css
modified: public/css/mainmenu.css
modified: template.html

[liuch]

I looked at your PR and I have a few comments:

• Twitchy animation of the menu button
• Header H1 jerks when the menu starts moving to the right
• Blank space at the top of activated menu, the position of the menu close button when the menu is active looks strange
• The button visually blends in with the adjacent header (h1) because of the same color
• Spaces in *.css and template.html files, there should be tabs as in the rest of the lines (code style)
• Trailing spaces in mainmenu.css (five lines)

Could you please fix that?

Just a couple more questions:

• Why was it necessary to change the animation?
• I also noticed that you replaced one
  element with three elements in the template.html file. Was there really a reason for that?