CSHARP-1015: fixed miscellaneous build warnings
added travis and appveyor build files. Updated readme to point at travis and appveyor for build badges.
added flowdock notification to travis.
CSHARP-1013: Initial commit.
CSHARP-1013: Renamed PingTime to RoundTripTime and Ping to Heartbeat.
CSHARP-1013: Added ExponentialWeightedMovingAverage to calculate AverageRoundTripTime.
CSHARP-1013: Support multiple credentials for backward compatibility.
CSHARP-1013: Use WriteConcern.Unacknowledged instead of null to represent unacknowledged write concern.
CSHARP-1013: Added tests for WriteConcern.
CSHARP-1013: Add tests for WValue classes.
CSHARP-1013: Turn on code analysis.
CSHARP-1013: Fixed code analysis warnings (except one still to be analyzed).
CSHARP-1013: Implement serialization of fields of custom exceptions.
CSHARP-1013: Suppress remaining code analysis warning that is a false positive.
CSHARP-1013: Add tests for custom exceptions.
CSHARP-1013: Added stubbed version of ClusterMonitorSpec (names to be refined as needed).
CSHARP-1013: Renamed NewClusterDescription to UpdateClusterDescription (New is not a verb...).
CSHARP-1013: Added tests for DeleteMessage.
CSHARP-1013: Added NSubstitute to the project and changed some of the DeleteMessageTests to use it.
CSHARP-1013: Added tests for the rest of the Messages.