Rename tracking to letterSpacing

defaultConfig.stub.js

@@ -49,7 +49,7 @@ module.exports = {
     textColors: ['responsive', 'hover', 'focus'],
     fontSize: ['responsive'],
     textStyle: ['responsive', 'hover', 'focus'],
-    tracking: ['responsive'],
+    letterSpacing: ['responsive'],
     userSelect: ['responsive'],
     verticalAlign: ['responsive'],
     visibility: ['responsive'],

defaultTheme.js

@@ -148,7 +148,7 @@ module.exports = function() {
       normal: 1.5,
       loose: 2,
     },
-    tracking: {
+    letterSpacing: {
       tight: '-0.05em',
       normal: '0',
       wide: '0.05em',

plugins/letterSpacing.js

@@ -0,0 +1 @@
+module.exports = require('../lib/plugins/letterSpacing').default

plugins/tracking.js

@@ -1 +0,0 @@
-module.exports = require('../lib/plugins/tracking').default

src/corePlugins.js

@@ -42,7 +42,7 @@ import textAlign from './plugins/textAlign'
 import textColors from './plugins/textColors'
 import fontSize from './plugins/fontSize'
 import textStyle from './plugins/textStyle'
-import tracking from './plugins/tracking'
+import letterSpacing from './plugins/letterSpacing'
 import userSelect from './plugins/userSelect'
 import verticalAlign from './plugins/verticalAlign'
 import visibility from './plugins/visibility'
@@ -113,7 +113,7 @@ export default function(config) {
     textColors,
     fontSize,
     textStyle,
-    tracking,
+    letterSpacing,
     userSelect,
     verticalAlign,
     visibility,