update readme

README.md

@@ -1,9 +1,66 @@
 # MiniRacer
 
-Minimal embedded V8 for Ruby
+Minimal, modern embedded V8 for Ruby.
+
+MiniRacer provides a minimal complete bridge to the V8 JavaScript engine from Ruby.
+
+It was created as an alternative to the excellent [therubyracer](https://github.com/cowboyd/therubyracer). Unlike therubyracer, mini_racer only implements a minimal (yet complete) bridge. This reduces the surface area making upgrading v8 much simpler and exahustive testing simpler.
+
+## Features
+
+### Simple eval for JavaScript
+
+You can simply eval one or many JavaScript snippets in a shared context
+
+```ruby
+context = MiniRacer::Context.new
+context.eval 'var adder = (a,b)=>a+b;'
+puts context.eval 'adder(20,22)'
+# => 42
+```
+
+### Attach global Ruby function to your JavaScript context
+
+You can attach one or many ruby proc that can be accessed via JavaScript
+
+```ruby
+context = MiniRacer::Context.new
+context.attach("adder", proc{|a,b| a+b})
+puts context.eval 'adder(20,22)'
+# => 42
+```
+
+### GIL free JavaScript execution
+
+The Ruby Global interpreter lock is released when scripts are executing
+
+```ruby
+context = MiniRacer::Context.new
+Thread.new do
+  sleep 1
+  context.stop
+end
+context.eval 'while(true){}'
+# => exception is raised
+```
+
+This allows you to execute multiple scripts in parallel.
+
+### Timeout support
+
+Contexts can specify a default timeout for scripts
+
+```ruby
+# times out after 1 second (1000 ms)
+context = MiniRacer::Context.new(timeout: 1000)
+context.eval 'while(true){}'
+# => exception is raised
+```
 
 ## Installation
 
+**Currently gem is in alpha development and can not be installed until libv8 is released**
+
 Add this line to your application's Gemfile:
 
 ```ruby

test/mini_racer_test.rb

@@ -70,7 +70,7 @@ class MiniRacerTest < Minitest::Test
 
   def test_es6_arrow_functions
     context = MiniRacer::Context.new
-    assert_equal 42, context.eval('a=()=>42; a();')
+    assert_equal 42, context.eval('adder=(x,y)=>x+y; adder(21,21);')
   end
 
   def test_attached_exceptions