Feat(Node 4): Add ProcessEnv interface

types/node/v4/index.d.ts

@@ -407,6 +407,10 @@ declare namespace NodeJS {
         isTTY?: true;
     }
 
+    export interface ProcessEnv {
+        [key: string]: string | undefined;
+    }
+
     export interface Process extends EventEmitter {
         stdout: Socket;
         stderr: Socket;
@@ -418,7 +422,7 @@ declare namespace NodeJS {
         chdir(directory: string): void;
         cwd(): string;
         debugPort: number;
-        env: any;
+        env: ProcessEnv;
         exit(code?: number): void;
         exitCode: number;
         getgid(): number;