Makes code forward compatible up to 0.3.0

Replaces nil documents with bson.D{{}}. Also removes accidental
renaming of options package. Fixes #2.

Author: tfogo

README.md

@@ -211,14 +211,14 @@ To find multiple documents, use `collection.Find()`. This method returns a `Curs
 
 ```go
 // Pass these options to the Find method
-options := options.Find()
-options.SetLimit(2)
+findOptions := options.Find()
+findOptions.SetLimit(2)
 
 // Here's an array in which you can store the decoded documents
 var results []*Trainer
 
-// Passing nil as the filter matches all documents in the collection
-cur, err := collection.Find(context.TODO(), nil, options)
+// Passing bson.D{{}} as the filter matches all documents in the collection
+cur, err := collection.Find(context.TODO(), bson.D{{}}, findOptions)
 if err != nil {
     log.Fatal(err)
 }
@@ -249,10 +249,10 @@ fmt.Printf("Found multiple documents (array of pointers): %+v\n", results)
 
 ### Delete Documents
 
-Finally, you can delete documents using `collection.DeleteOne()` or `collection.DeleteMany()`. Here you pass `nil` as the filter argument, which will match all documents in the collection. You could also use [`collection.Drop()`](https://godoc.org/github.com/mongodb/mongo-go-driver/mongo#Collection.Drop) to delete an entire collection.
+Finally, you can delete documents using `collection.DeleteOne()` or `collection.DeleteMany()`. Here you pass `bson.D{{}}` as the filter argument, which will match all documents in the collection. You could also use [`collection.Drop()`](https://godoc.org/github.com/mongodb/mongo-go-driver/mongo#Collection.Drop) to delete an entire collection.
 
 ```go
-deleteResult, err := collection.DeleteMany(context.TODO(), nil)
+deleteResult, err := collection.DeleteMany(context.TODO(), bson.D{{}})
 if err != nil {
     log.Fatal(err)
 }

main.go

@@ -81,14 +81,13 @@ func main() {
 
 	fmt.Printf("Found a single document: %+v\n", result)
 
-	// Add extra options to queries using the options package
-	options := options.Find()
-	options.SetLimit(2)
+	findOptions := options.Find()
+	findOptions.SetLimit(2)
 
 	var results []*Trainer
 
 	// Finding multiple documents returns a cursor
-	cur, err := collection.Find(context.TODO(), nil, options)
+	cur, err := collection.Find(context.TODO(), bson.D{{}}, findOptions)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -114,10 +113,11 @@ func main() {
 	fmt.Printf("Found multiple documents (array of pointers): %+v\n", results)
 
 	// Delete all the documents in the collection
-	deleteResult, err := collection.DeleteMany(context.TODO(), nil)
+	deleteResult, err := collection.DeleteMany(context.TODO(), bson.D{{}})
 	if err != nil {
 		log.Fatal(err)
 	}
+
 	fmt.Printf("Deleted %v documents in the trainers collection\n", deleteResult.DeletedCount)
 
 	// Close the connection once no longer needed