Added ModelMistral and made it default for OLLAMA (#90)

Add the Mistral model to the Ollama backend and make it the default,
as it outperforms codellama.

libaiac/ollama/models.go

@@ -35,6 +35,9 @@ var (
 	// ModelCodeBooga represents the codebooga model
 	ModelCodeBooga = types.Model{"codebooga", 0, types.ModelTypeChat}
 
+	// ModelMistral represents the mistral model
+	ModelMistral = types.Model{"mistral", 0, types.ModelTypeChat}
+
 	// SupportedModels is a list of all language models supported by this
 	// backend implementation.
 	SupportedModels = []types.Model{
@@ -48,6 +51,7 @@ var (
 		ModelStableCode,
 		ModelMagicoder,
 		ModelCodeBooga,
+		ModelMistral,
 	}
 )
 
@@ -59,5 +63,5 @@ func (client *Client) ListModels() []types.Model {
 
 // DefaultModel returns the default model used by this backend.
 func (client *Client) DefaultModel() types.Model {
-	return ModelCodeLlama
+	return ModelMistral
 }