Smarter delim chunker

I was having some issues reading in a large json-blob file, and noticed that we read the entire thing into memory. It's better to read it in chunks, since we are yielding them anyways. I also hit come encoding issues, so I've added `kwargs` to the `analyze` method that can be passed into the `json.loads`. Finally, I noticed it was incorrectly counting the number of blobs, and this originated in having `enumerate` start at 0. 

1. Adding smarter chunker so it can read larger files; 
2. adding `kwargs` for encoding issues
3. starting the enumerater at 1 to correctly count the number of blobs

@wrobstory for review please!
Off by one errors are my speciality.