Update README.md

Removed quick reference.
Added link to project wiki where measure descriptions can be found.
Update README.md

* Systems for comparison => https://github.com/benhachey/conll03_nel_eval/wiki/Benchmark-results
* System output format => https://github.com/benhachey/conll03_nel_eval/wiki/data%20format
Update README.md

Filtering datasets => https://github.com/benhachey/conll03_nel_eval/wiki/Usage
Refactored data to model Documents, Sentences, Mentions and Tokens (the latter two Spans).
Evaluation uses a hashing technique and should be faster.
Mappings now use underscores, as per original AIDA data.
Removed two nil evaluations.
Changed spaces to underscores for the API mapping data.
Merge branch 'data-rewrite'
tidying, hoffart compatibility, debugging entity_match
Towards significance testing
Significance testing with approximate randomization