don't divide by 0.
Merge branch 'master' of github.com:wangjohn/entity_resolution
Floats
Merge branch 'master' of github.com:wangjohn/entity_resolution
Fixed or notation.
Merge branch 'master' of github.com:wangjohn/entity_resolution

Conflicts:
	distances.py
Merge branch 'master' of github.com:wangjohn/entity_resolution
Merge branch 'master' of github.com:wangjohn/entity_resolution
Minor adjustments on matcher.