Introduce DB::ConnectionContext (#44)

* make Database a ConnectionContext.
* introduce SingleConnectionContext for independant connections.
* add `DB#connect` to create non pooled connections.

spec/custom_drivers_types_spec.cr

@@ -43,8 +43,8 @@ class FooDriver < DB::Driver
     @@row
   end
 
-  def build_connection(db : DB::Database) : DB::Connection
-    FooConnection.new(db)
+  def build_connection(context : DB::ConnectionContext) : DB::Connection
+    FooConnection.new(context)
   end
 
   class FooConnection < DB::Connection
@@ -106,8 +106,8 @@ class BarDriver < DB::Driver
     @@row
   end
 
-  def build_connection(db : DB::Database) : DB::Connection
-    BarConnection.new(db)
+  def build_connection(context : DB::ConnectionContext) : DB::Connection
+    BarConnection.new(context)
   end
 
   class BarConnection < DB::Connection

spec/db_spec.cr

@@ -25,6 +25,25 @@ describe DB do
     connections.first.closed?.should be_true
   end
 
+  it "should create a connection and close it" do
+    DummyDriver::DummyConnection.clear_connections
+    DB.connect "dummy://localhost" do |cnn|
+      cnn.should be_a(DummyDriver::DummyConnection)
+    end
+    connections.size.should eq(1)
+    connections.first.closed?.should be_true
+  end
+
+  it "should create a connection and wait for explicit closing" do
+    DummyDriver::DummyConnection.clear_connections
+    cnn = DB.connect "dummy://localhost"
+    cnn.should be_a(DummyDriver::DummyConnection)
+    connections.size.should eq(1)
+    connections.first.closed?.should be_false
+    cnn.close
+    connections.first.closed?.should be_true
+  end
+
   it "query should close result_set" do
     with_witness do |w|
       with_dummy do |db|

spec/dummy_driver.cr

@@ -2,13 +2,13 @@ require "spec"
 require "../src/db"
 
 class DummyDriver < DB::Driver
-  def build_connection(db : DB::Database) : DB::Connection
-    DummyConnection.new(db)
+  def build_connection(context : DB::ConnectionContext) : DB::Connection
+    DummyConnection.new(context)
   end
 
   class DummyConnection < DB::Connection
-    def initialize(db)
-      super(db)
+    def initialize(context)
+      super(context)
       @connected = true
       @@connections ||= [] of DummyConnection
       @@connections.not_nil! << self