Add spec for DB.connect

Update to crystal-db ~> 0.4.0

spec/connection_spec.cr

@@ -57,4 +57,15 @@ describe Connection do
       end
     end
   end
+
+  it "opens a connection without the pool" do
+    with_cnn do |cnn|
+      cnn.should be_a(SQLite3::Connection)
+
+      cnn.exec "create table person (name string, age integer)"
+      cnn.exec "insert into person values (\"foo\", 10)"
+
+      cnn.scalar("select count(*) from person").should eq(1)
+    end
+  end
 end

spec/spec_helper.cr

@@ -12,6 +12,13 @@ ensure
   File.delete(DB_FILENAME)
 end
 
+def with_cnn(&block : DB::Connection ->)
+  File.delete(DB_FILENAME) rescue nil
+  DB.connect "sqlite3:#{DB_FILENAME}", &block
+ensure
+  File.delete(DB_FILENAME)
+end
+
 def with_db(name, &block : DB::Database ->)
   File.delete(name) rescue nil
   DB.open "sqlite3:#{name}", &block