added support for document mapping

document/mapping.go

@@ -0,0 +1,13 @@
+package document
+
+import (
+	"github.com/couchbaselabs/bleve/analysis"
+)
+
+type FieldMapping struct {
+	Name     string
+	Options  IndexingOptions
+	Analyzer *analysis.Analyzer
+}
+
+type Mapping map[string]*FieldMapping