Making Gutter Grid more IE11 friendly

This is a big update. CSS Grid is killing off almost all need for Gutter Grid. IE 11 is essentially the only reason why Gutter Grid is still at all worth using right now. With IE 8 and 9 being essentially dead, it doesn't make sense to hamper the experience of IE11 developers for the sake of these old browsers now.

I'm optimising the code to make the experience as enjoyable as possible for IE11 devs. Unfortunately it means the defaults will be different depending on if $grid-legacy-support is enabled or not.
If the legacy setting is turned on then Gutter Grid will behave in mostly the same way as it did in version 3.x.

Breaking changes:

Note: these breaking changes mostly apply only when the $grid-legacy-support is set to false (the default setting).

• New default settings

  • $align in the mixin now defaults to left.
  • $wrap in the mixin now defaults to true but only if $cols has been defined.
  • Grids no longer stretch by default. In order to make the grid stretch like it did in v3.x, if using the classes system, a grid--stretch class needs to be added to the .grid element. If using the mixin system, a $stretch: true setting needs to be called in the mixin. This is only necessary if columns have been defined.
  • Grids with a column count setting will now wrap by default unless if wrapping is explicitly disabled or $grid-legacy-support is enabled.

• The grid--noGrowth class has been renamed grid--noStretch to align with the new grid--stretch class. (A breaking change for everyone).

• The $grow setting in the mixin has been renamed to $stretch. (A breaking change for everyone).

• Multi-spanning cells now flex-grow by default. (A breaking change for everyone).

• $breakpoints parameter in the mixin has been moved to the 3rd slot. (A breaking change for everyone).

• $grid-break-points setting now has new syntax that makes it easier to tell what column count a particular set of breakpoints is for. Below is an impracticle example showing the new format:

  Version 3.x

  $grid-break-points: (
    // No media queries for 1 column grid
    (false),
  
    // 2 column grid breakpoints
    (
      // At 600px wide screen and below, make columns 100% wide
      100%: 600px,
    ),
  
    // No media queries for 3 column grid
    (false),
  
    // 4 column grid breakpoints
    (
      50% : 960px,
      100% : 600px,
    )
  
    // No media queries for a 5 column grid
    false,
  )

  Version 4.0.0

  $grid-break-points: (
    // No need to mention a 1 column grid
  
    // 2 column grid breakpoints
    2: (
      // At 600px wide screen and below, make it a 1 column grid
      // (using percentages here instead of column count still works)
      1: 600px,
    ),
  
    // No need to mention a 3 column grid
  
    // 4 column grid breakpoints
    4: (
      2 : 960px,
      1 : 600px,
    )
  
    // No media queries for 5 column grid
    // Only needed if using the class system
    5: false,
  )

New features:

• Instead of listing percentage values as keys in the $breakpoints parameter key/value pairs, you can now simply list the number of columns that the grid should have as the keys in the key/value pairs. The old method of using percentages as the key values will still work if that method is preferred.

  Version 3.x (Still works in version 4)

  @include grid(7, $breakpoints: (
    // On a 960px wide screen or below, the columns will be 25% wide
    25% : 960px,
    // You can use mq-scss syntax here as well
    50% : (max, 600px),
    100% : 480px,
  ));

  Version 4.x

  @include grid(7, $breakpoints: (
    //On a 960px wide screen or below, there will be 4 columns
    4 : 960px,
    // You can still use mq-scss syntax here as well
    2 : (max, 600px),
    1 : 480px,
  ));

• calc is now used by default to determine column widths. So instead of seeing width: 33.33%; in your styles, you will see width: calc(100% / 3);. This makes it clear from the styles how many columns are being generated. For example it is much clearer that width: calc(100% / 7); equals 7 columns rather than width: 14.2857%;.

• New config variable $grid-calc-support has been introduced. Since calc isn't supported in every browser (thanks Opera Mini and Android 4) a new $grid-calc-support setting has been added. This defaults to whatever the opposite of the $grid-legacy-support setting is. This means that if legacy support is needed then $grid-calc-support will automatically be disabled. If you need to support Opera Mini (or you prefer seeing percentages in your styles), set $grid-calc-support to false.