Env (turbine 0.1 API)

All Known Implementing Classes:

CompoundEnv, LazyEnv, SimpleEnv
```
public interface Env<S extends Symbol,V>
```
An environment that maps Symbols S to bound nodes V.
For example, BoundClass represents superclasses as a ClassSymbol, which only contains the binary name of the type. To get the BoundClass for that supertype, an Env<BoundClass> is used.
The indirection through env makes it possible to represent a graph with cycles using immutable nodes, and makes it easy to reason about the information produced and consumed by each pass.
TODO(cushon): keep an eye on the cost of indirections, and consider caching lookups in bound nodes if it looks like it would make a difference.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`@Nullable V`	`get(S sym)`	Returns the information associated with the given symbol in this environment.
`default V`	`getNonNull(S sym)`

- Method Detail
  - get
```
@Nullable V get(S sym)
```
    Returns the information associated with the given symbol in this environment.
  - getNonNull
```
default V getNonNull(S sym)
```