Some doc improvements

[alexvy86]

Description

Improvements to documentation. Typos, formatting, capitalizing Container.

Some things where I'd like some feedback to make sure things are accurate and clear:

• Pointing out that calling serialize() on an attached container is an error (the code will currently fail an assert()).
  • Tangent: is this "internal enough" that an assert is preferable to throwing a UsageError?
• Description for the Container class.