function _moveSkippingWhitespace(moveFxn, ctx) {
        if (!moveFxn(ctx)) {
            return false;
        }
        while (!ctx.token.className && ctx.token.string.trim().length === 0) {
            if (!moveFxn(ctx)) {
                return false;
            }
        }
        return true;
    }
@private
moves the current context in the given direction, skipping any whitespace it hits
@param {function} moveFxn the funciton to move the context
@param {editor:{CodeMirror}, pos:{ch:{string}, line:{number}}, token:{object}} ctx
@return {boolean} whether the context changed