Merge pull request #10 from SwiftPackageIndex/hashable

Make ShellOutCommand hashable as well

Author: finestructure

Sources/ShellOutCommand.swift

@@ -1,5 +1,5 @@
 /// Structure used to pre-define commands for use with ShellOut
-public struct ShellOutCommand: Equatable {
+public struct ShellOutCommand: Equatable, Hashable {
     /// The string that makes up the command that should be run on the command line
     public var command: String