Sqlite-transform

- Better `--help` for `sqlite-transform lambda`. [7](https://github.com/simonw/sqlite-transform/issues/7)

- `return` is now optional for one-line lambdas, e.g.

sqlite-transform lambda my.db mytable mycolumn --code='str(value).upper()'

- Added `lambda` command, which lets you specify a Python expression (or multiple lines of code) to be executed against every value in the column. [Documentation here](https://github.com/simonw/sqlite-transform/blob/0.2/README.md#lambda-for-executing-your-own-code). (2)
- Added a `parsedate` command, which works like `parsedatetime` except it outputs just the date component. (1)

- First release, supporting only the `parsedatetime` command.