Add "import Dispatch" for Linux builds, update Linux instructions for Swift 3.0.2.

Examples/Echo/Swift/Generated/echo.server.pb.swift

@@ -41,6 +41,7 @@
 
 import Foundation
 import gRPC
+import Dispatch
 
 /// Type for errors thrown from generated server code.
 public enum Echo_EchoServerError : Error {

Examples/Echo/Swift/SwiftPM/Sources/main.swift

@@ -32,6 +32,7 @@
  */
 import Foundation
 import gRPC
+import Dispatch
 
 print("\(CommandLine.arguments)")
 
@@ -189,6 +190,3 @@ if client != "" {
   }
   
 }
-
-
-

LINUX.md

@@ -33,9 +33,9 @@ Start a docker instance with the following command:
     # go to /root
     cd
     # download and unpack swift
-    wget https://swift.org/builds/swift-3.0.1-release/ubuntu1604/swift-3.0.1-RELEASE/swift-3.0.1-RELEASE-ubuntu16.04.tar.gz
-    tar xzf swift-3.0.1-RELEASE-ubuntu16.04.tar.gz
-    ln -s swift-3.0.1-RELEASE-ubuntu16.04 swift
+    wget https://swift.org/builds/swift-3.0.2-release/ubuntu1604/swift-3.0.2-RELEASE/swift-3.0.2-RELEASE-ubuntu16.04.tar.gz
+    tar xzf swift-3.0.2-RELEASE-ubuntu16.04.tar.gz
+    ln -s swift-3.0.2-RELEASE-ubuntu16.04 swift
 
 ## Add Swift to your path
     # add swift to your path by adding this to your .bashrc

Plugin/swiftgrpc.templates/server.pb.swift

@@ -41,6 +41,7 @@
 
 import Foundation
 import gRPC
+import Dispatch
 //-{% for service in protoFile.service %}
 
 /// Type for errors thrown from generated server code.