added a visitor for Set objects
Fixed typos
Merge pull request #181 from prathamesh-sonpatki/typos

Fixed typos
call super from initialize
record who created the node when $DEBUG is true
"Relational Database Managements systems", not "Relational Database Managements System systems"
Prettied up the README with syntax highlighting.

[ci skip]
Merge pull request #193 from parndt/patch-1

Prettied up the README with syntax highlighting. [ci skip]
Remove deprecated `Arel::Table.table_cache` with no replacement
Remove deprecated `Arel::Table#columns` with no replacement
Add licences to gemspec

Closes #197
Cache visitor dispatch on a per-visitor basis
Improve performance of #uniq across a large number of nodes
Merge pull request #206 from SamSaffron/master

Improve performance of #uniq across a large number of nodes
Merge pull request #204 from trptcolin/visitor_dispatch_caching

Cache visitor dispatch on a per-visitor basis
Support `columns_for_distinct`
fix one deprecation warning
Merge pull request #211 from yahonda/support_columns_for_distinct_oracle

Support `columns_for_distinct` with Oracle adapter
Release 4.0.1
Fix warning of shadowing variable