Reader/Writer extension methods

- Created IObjectReader extension methods to wrap some common read
patterns (Resolves issue #1).
- Removed ReadStartObject and ReadStartArray IObjectWriter extension
methods, as they hid some internals of the writer in a confusing syntax.
Create a Nuget package

Resolves issue #2.
Merge branch 'master' of https://github.com/hotchai/serialize.net