0.4 release

[alekseykulikov]

• improve db.use()
• add schema.dropStore() and schema.dropIndex()
• onversionchange Version changes in multi-window app #16
• improve tests
• fix iOS 8 & Safari 7.0.6, IE10 & IE11 support (add this to Readme) Problem in Safari 7.1 and 8 #17
• improve docs for store.cursor (docs for schema.drop*) Production ready? #14

[alekseykulikov]

Thanks @unkillbob to helping with new release, I've added you as collaborator for this project.
I've disabled transaction reuse feature, because it needed better implementation.
Currently working on 0.5.0 in https://github.com/treojs in the aim to make treo more modular and stable.