Add docker containers to test services.

This commit initializes the needed services which are not mocked
so tests can be executed in any environment with docker.

Some default modifications (i.e: connection strings) were also made to
current tests to accomodate them for this setup.

A docker-compose.yml file is provided with all the necessary parameters
for this services to be initialized. Future services can be added
easily by extending this configuration file

In addition a makefile has been introduced to simplify command execution

plugins/postgresql/postgresql_test.go

@@ -12,7 +12,7 @@ func TestPostgresqlGeneratesMetrics(t *testing.T) {
 	p := &Postgresql{
 		Servers: []*Server{
 			{
-				Address:   "sslmode=disable",
+				Address:   "host=localhost user=postgres sslmode=disable",
 				Databases: []string{"postgres"},
 			},
 		},
@@ -57,7 +57,7 @@ func TestPostgresqlTagsMetricsWithDatabaseName(t *testing.T) {
 	p := &Postgresql{
 		Servers: []*Server{
 			{
-				Address:   "sslmode=disable",
+				Address:   "host=localhost user=postgres sslmode=disable",
 				Databases: []string{"postgres"},
 			},
 		},
@@ -78,7 +78,7 @@ func TestPostgresqlDefaultsToAllDatabases(t *testing.T) {
 	p := &Postgresql{
 		Servers: []*Server{
 			{
-				Address: "sslmode=disable",
+				Address: "host=localhost user=postgres sslmode=disable",
 			},
 		},
 	}