updating readme

Author: geelen

README.md

@@ -3,6 +3,11 @@
 
 ## API
 
+```js
+import Core from 'css-modules-loader-core'
+let core = new Core()
+```
+
 ### core.load( sourceString , sourcePath , pathFetcher ) =><br>&nbsp;&nbsp;Promise({ injectableSource, exportTokens })
 
 Processes the input CSS `sourceString`, looking for dependencies such as `@import` or `:import`. Any localisation will happen by prefixing a sanitised version of `sourcePath` When dependencies are found, it will ask the `pathFetcher` for each dependency, resolve & inline any imports, and return the following object:
@@ -12,22 +17,21 @@ Processes the input CSS `sourceString`, looking for dependencies such as `@impor
 
 These should map nicely to what your build-tool-specific loader needs to do its job.
 
-### core.plugins = pluginArray
+### new Core([plugins])
 
 The default set of plugins is [[postcss-modules-local-by-default](https://github.com/css-modules/postcss-modules-local-by-default), [postcss-modules-extract-imports](https://github.com/css-modules/postcss-modules-extract-imports), [postcss-modules-scope](https://github.com/css-modules/postcss-modules-scope)] (i.e. the CSS Modules specification). This can override which PostCSS plugins you wish to execute, e.g.
 
 ```js
-import core from 'css-loader-core'
+import Core from 'css-loader-core'
 import autoprefixer from 'autoprefixer'
 import colorFunctions from 'postcss-color-function'
 
 // Don't run local-by-default, but use colorFunctions 
 // beforehand and autoprefixer afterwards:
-core.plugins = [
+let core = new Core([
   colorFunctions, 
   core.plugins.extractImports, 
   core.plugins.scope, 
   autoprefixer("Last 2 Versions")
-]
+])
 ```
-