@mixin respond-min($width) {
    @if $ie-version < 9 {
        @content;
    }
    @else {
        @media screen and (min-width: $width) {
            @content;
        }
    }
}

@mixin respond-max($width) {
    @if $ie-version < 9 {
        @if $width >= $screen-medium {
            @content;
        }
    }
    @else {
        @media screen and (max-width: $width - 1) {
            @content;
        }
    }
}

@mixin respond-min($width) {
    @if $ie-version < 9 {
        @content;
    }
    @else {
        @media screen and (min-width: $width) {
            @content;
        }
    }
}

@mixin respond-max($width) {
    @if $ie-version < 9 {
        @if $width >= $screen-medium {
            @content;
        }
    }
    @else {
        @media screen and (max-width: $width - 1) {
            @content;
        }
    }
}

@mixin respond-min-max($min-width, $max-width) {
    @if $ie-version < 9 {
        @if $max-width >= $screen-medium {
            @content;
        }
    }
    @else {
        @media screen and (min-width: $min-width) and (max-width: $max-width - 1) {
            @content;
        }
    }
}

Add mixin for min-width and max-width MQs.
Add mixin for min-width and max-width MQs.
