Incorrect number of embedding dimensions in the YAML schema in README.md

[mirekphd]

The sample schema in the YAML format presented in the README.md file in this section contains an incorrect number of embedding dimensions in the dims key - they should be changed from 3 to 4 to work with the rest of the example.

Published version:

index:
[..]
fields:
[..]
    attrs:
      algorithm: flat
      dims: 3
      distance_metric: cosine
      datatype: float32

... should be:

index:
[..]
fields:
[..]
    attrs:
      algorithm: flat
      dims: 4
      distance_metric: cosine
      datatype: float32

[tylerhutcherson]

Thanks, this will be fixed here: #200