Logging

You can turn on LightService logging with this setting:

```ruby
LightService::Configuration.logger = Logger.new(STDOUT)
```

You will have something like this:
```bash
I, [2014-08-06T21:02:52.765278 #44103]  INFO -- : [LightService] - calling organizer <TestDoubles::MakesTeaAndCappuccino>
I, [2014-08-06T21:02:52.765330 #44103]  INFO -- : [LightService] -     keys in context: :tea, :milk, :coffee
I, [2014-08-06T21:02:52.765390 #44103]  INFO -- : [LightService] - executing <TestDoubles::MakesTeaWithMilkAction>
I, [2014-08-06T21:02:52.765415 #44103]  INFO -- : [LightService] -   expects: :tea, :milk
I, [2014-08-06T21:02:52.765430 #44103]  INFO -- : [LightService] -   promises: :milk_tea
I, [2014-08-06T21:02:52.765462 #44103]  INFO -- : [LightService] -     keys in context: :tea, :milk, :coffee, :milk_tea
I, [2014-08-06T21:02:52.765511 #44103]  INFO -- : [LightService] - executing <TestDoubles::MakesLatteAction>
I, [2014-08-06T21:02:52.765533 #44103]  INFO -- : [LightService] -   expects: :coffee, :milk
I, [2014-08-06T21:02:52.765547 #44103]  INFO -- : [LightService] -   promises: :latte
I, [2014-08-06T21:02:52.765561 #44103]  INFO -- : [LightService] -     keys in context: :tea, :milk, :coffee, :milk_tea, :latte
```

It also logs `failures` and `skip_alls`.

```bash
I, [2014-08-06T21:05:38.548453 #44507]  INFO -- : [LightService] - calling organizer <TestDoubles::MakesCappuccinoAddsTwoAndFails>
I, [2014-08-06T21:05:38.548477 #44507]  INFO -- : [LightService] -     keys in context: :milk, :coffee
W, [2014-08-06T21:05:38.548524 #44507]  WARN -- : [LightService] - :-((( <TestDoubles::MakesLatteAction> has failed...
W, [2014-08-06T21:05:38.548541 #44507]  WARN -- : [LightService] - context message: Can't make a latte from a milk that's too hot!
```
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