Refactor and use StreamPeer interface

[ashtonmeuser]

• Split source files up. Should make things more maintainable as project grows.
• Allow reading from & writing to Wasm module memory using StreamPeer interface. Also adopted some methods from StreamPeerBuffer e.g. seek.
• Split original load method into compile and instantiate. Behaviour of load remains the same (it calls compile and instantiate). Separating these allows inspection before instantiation which will be important for support of imports.
• Module inspection via inspect now returns memory limits and, if instantiated, current memory allocation.

To do:

• [x] Settle on a better name than reader for the StreamPeer.
• [x] Update docs.

CC @Trey2k since this is no longer for an audience of one. Happy to hear any feedback.

[Trey2k]

This PR looks great, love to see src folder added. And use of a StreamPeer makes sense to me.

[ashtonmeuser]

Much appreciated.

love to see src folder added

Yeah... This was very much a POC until it actually kinda showed potential.