Remove entries from shards info file when pruning (#368)

spec/integration/prune_spec.cr

@@ -23,7 +23,7 @@ describe "prune" do
   it "removes unused dependencies" do
     Dir.cd(application_path) { run "shards prune" }
     installed_dependencies.should eq(["web"])
-    File.exists?(File.join(application_path, "lib", "orm.sha1")).should be_false
+    Shards::Info.new(install_path).installed.keys.should eq(["web"])
   end
 
   it "removes directories" do

src/commands/prune.cr

@@ -16,15 +16,12 @@ module Shards
             Log.debug { "rm -rf '#{Helpers::Path.escape(path)}'" }
             FileUtils.rm_rf(path)
 
-            version_file = "#{path}.version"
-            if File.exists?(version_file)
-              Log.debug { "rm '#{Helpers::Path.escape(version_file)}'" }
-              File.delete(version_file)
-            end
-
+            Shards.info.installed.delete(name)
             Log.info { "Pruned #{File.join(File.basename(Shards.install_path), name)}" }
           end
         end
+
+        Shards.info.save
       end
     end
   end