Green Mountain (GMCR) says its founder and chairman Robert Stiller and fellow director William Davis were forced to resign from the board today because of margin calls that required them to divest of millions of shares of their stock. GMCR calls these forced sales " disappointing" and "beyond the control of the company" and said it was in the best interest of shareholders for the two to "relinquish their leadership positions." Shares -4.3% AH