add section on Dialects to the documentation. For now, it only has info on PostgreSQL, but this can be extended later to include information on the other supported dialects. (#1759)

documents/SUMMARY.md

@@ -32,4 +32,6 @@
 * [Development](development.md)
   * [Architecture](development.md#architecture)
   * [Write Plugins](development.md#write-plugins)
+* [Dialects](dialects.md)
+  * [Dialect Specific Columns](dialects.md#dialect-specific-columns)
 * [Change Log](changelog.md)

documents/dialects.md

@@ -0,0 +1,58 @@
+# Dialects
+
+<!-- toc -->
+
+## Dialect Specific Columns
+
+Certain dialects of SQL ship with their own custom, non-standard column types, such as the ```jsonb``` column in PostgreSQL. GORM supports loading several of such types, as listed in the following sections.
+
+#### PostgreSQL
+GORM supports loading the following PostgreSQL exclusive column types:
+- jsonb
+- hstore
+
+Given the following Model definition: 
+````go
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"github.com/jinzhu/gorm"
+	"github.com/jinzhu/gorm/dialects/postgres"
+)
+
+type Document struct {
+	Metadata    postgres.Jsonb	    
+	Secrets     postgres.Hstore     
+	Body        string
+
+	ID          int   
+}
+````
+
+You may use the model like so: 
+
+````go
+password := "0654857340"
+metadata := json.RawMessage(`{"is_archived": 0}`)
+sampleDoc := Document{
+    Body : "This is a test document",
+    Metadata : postgres.Jsonb{ metadata },
+    Secrets : postgres.Hstore{"password" : &password },
+}
+
+//insert sampleDoc into the database
+db.Create(&sampleDoc)
+
+//retrieve the fields again to confirm if they were inserted correctly
+resultDoc := Document{}
+db.Where("id = ?", sampleDoc.ID).First(&resultDoc)
+
+metadataIsEqual := reflect.DeepEqual( resultDoc.Metadata, sampleDoc.Metadata)
+secretsIsEqual := reflect.DeepEqual( resultDoc.Secrets, resultDoc.Secrets)
+
+//this should print "true"
+fmt.Println("Inserted fields are as expected:", metadataIsEqual && secretsIsEqual)
+
+```` 
+