Resolving issue 14 and 15

Resolving issue #14:

• Metadata requests were not retried and hence often failed. Messages like NoInstanceID were cached.
• Now properly attempts 10 times with 2 second timeout.
• Error messages may still result as pattern output but this is transient once metadata can be collected.

Resolving issue #15

• MessageParsers can be replaced. DummyLogEventMessageParser is provided for convenience.
• This resolves the problem when you really want reserved keynames to appear in the message, as in Message: my important message.