Added release notes for 1.9.1.

Author: rstam

Diff for: CSharpDriver.sln

@@ -67,6 +67,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Release Notes", "Release No
 		Release Notes\Release Notes v1.8.2.md = Release Notes\Release Notes v1.8.2.md
 		Release Notes\Release Notes v1.8.3.md = Release Notes\Release Notes v1.8.3.md
 		Release Notes\Release Notes v1.8.md = Release Notes\Release Notes v1.8.md
+		Release Notes\Release Notes v1.9.1.md = Release Notes\Release Notes v1.9.1.md
 		Release Notes\Release Notes v1.9.md = Release Notes\Release Notes v1.9.md
 	EndProjectSection
 EndProject

Diff for: Release Notes/Release Notes v1.9.1.md

@@ -1,2 +1,42 @@
 C#/.NET Driver Version 1.9.1 Release Notes
-==========================================
+==========================================
+
+This is a minor release which fixes some issues reported since 1.9.0 was released. It is a recommended
+upgrade for anyone using 1.9.0.
+
+An online version of these release notes is available at:
+
+https://github.com/mongodb/mongo-csharp-driver/blob/v1.x/Release%20Notes/Release%20Notes%20v1.9.1.md
+
+The full list of JIRA issues resolved in this release is available at:
+
+https://jira.mongodb.org/issues/?filter=15166
+
+Documentation on the C# driver can be found at:
+
+http://www.mongodb.org/display/DOCS/CSharp+Language+Center
+http://api.mongodb.org/csharp/current/
+
+General Changes
+===============
+
+The 1.9.x releases will be the last non-bug fix release supporting .NET 3.5.
+
+The issues fixed in 1.9.1 are:
+
+* [LINQ queries against BsonValue properties whose value is C# null](https://jira.mongodb.org/browse/CSHARP-932)
+* [$maxDistance must go inside $near when using GeoJson data](https://jira.mongodb.org/browse/CSHARP-950)
+* [Allow ParallelScan to go to secondaries](https://jira.mongodb.org/browse/CSHARP-955)
+* [Allow Aggreagate to go to secondaries as long as the pipeline doesn't contain $out](https://jira.mongodb.org/browse/CSHARP-956)
+* [Support automatically setting the _id even when using an interface as the document type](https://jira.mongodb.org/browse/CSHARP-958)
+* [Don't consider any wnote and jnote values to be errors](https://jira.mongodb.org/browse/CSHARP-959)
+* [Fixed a stack overflow when deserializing an interface with a missing _t discriminator value](https://jira.mongodb.org/browse/CSHARP-961)
+* [Added SetBits to IndexOptions builder](https://jira.mongodb.org/browse/CSHARP-962)
+* [JsonReader support for new $date format with ISO8601 strings as used by 2.6 version mongoexport](https://jira.mongodb.org/browse/CSHARP-963)
+
+Compatibility Changes
+---------------------
+
+There were no intentional backwards breaking changes.  If you come across any,
+please inform us as soon as possible by email [email protected] or by reporting 
+an issue at jira.mongodb.com.