Update Transmit cask to v4.4.1 from v4.4.0

This patch updates the version of Transmit to version 4.4.1 from the
current version of 4.4.0. It includes a new checksum, version, and URL.

Audit:
```sh
❯ brew cask audit transmit
audit for transmit: passed
```

Let me know if there's anything I missed and I'd be happy to fix it.

For reference, v4.4.1 has the following [upgrade notes][]:

* Fixed a potential crash when using Transmit Disk on a non-admin account
* Fixed Growl support on 10.6
* Fixed an issue where NFS shares would not appear properly in the browser
* Improved DockSend reliability when dragging multiple folders and files
* Improved Retina compatibility

[upgrade notes]: http://www.panic.com/transmit/releasenotes.html