TODO: updated with new ideas

indexer/bi-gram-fuzzy-index:
    - changed the structure of the return value, now returns
      the index as list items instead of a single object

store/db:
    -added a few docstrings

store/index:
    - functions for loading, merging and saving the index, needs lots of work

store/store:
    - added a couple of attributes
    - defined store-integrity-error as a subtype of error
    - defined the function check-store(), will eventually return the
      aforementioned error
    - changed directory structure of store, all parts of the index go
      in a single directory