Initial support for Rails 4.2

This commit supports following changes, still it needs to support date/time features such as `set_date_columns`

- BindSubstitution class removed
https://github.com/rails/rails/commit/ee54e9bb3a6d7ffcf756ec1e385399b92354cb6b#diff-c226a4680f86689c3c170d4bc5911e96

- Delegate `Column#type` to the injected type object
https://github.com/rails/rails/commit/0b682e4b05c8f58c77c655650af6638c483ac903
Merge pull request #464 from yahonda/initial_support_rails42

Initial support for Rails 4.2