[Minor Changes and Fixes]

    -    Added a new Theorem Environment (Lemma)
    -    Added a new Math Operator for Gradient (\grad)
    -    Changed the salnote baseclass to koma-script article
         (scrartcl) rather the ams article class (amsart)
    -    Made a more compact heading for salnote class - more
         improvements on the way
    -    Changed the margins to salnote class
    -    changed the font to the charter font, it looks better