point out the power connector may be green or blue

some pictures show a blue power connector on the shield, others show green.  Mine was green so just updating the text so folks aren't looking for a blue header to put the wires into.
adding some detail on how to Jog each axis

just adding a few words on how to find the buttons to jog the axes using the Universal Gcode sender
Merge pull request #2 from lordmundi/gh-pages

minor updates to electronics content