limit inline options to endpoint, protocol, and headers

[loomis]

Limit the inline options to endpoint, protocol, and headers. If other options are needed, then the configuration with the options object should be used.

Update the example program to use the options object and correct collector configuration.

Fixes #61.

[nblumhardt]

Looking at this again, how would you feel about leaving headers out, too? Keep it super, super simple? The Serilog.Settings.Configuration feature set won't support dictionary args as things stand, anyway, I think.

[loomis]

Most real use cases will be using an authenticated endpoint, so they won't be able to use the inline configuration. That's OK with me though. Realistically, I think most people should be using the options interface instead.

[nblumhardt]

👍 I think real-world use will also almost always specify resource attributes; I'm leaning in the same direction (towards the options interface) too.