Pattern matching on string setting doesn't compile

```
Environment.value match {
      case "dev" => 
```

fails with:

```
build.sbt:81: error: type mismatch;
 found   : String("dev")
 required: sbt.Def.Setting[String]
      case "dev" => 
```

but

```
Environment.value.value match {
      case "dev" =>
```

fails with

```
build.sbt:80: error: value value is not a member of String
    Environment.value.value match {
```
