Release 1.6.1

```
Bob the Builder (1):
      Stirling 1.6.1-SNAPSHOT

Jussi Virtanen (5):
      Add Netstring support
      Add Netstring text support
      Use Netstring in NASDAQ OMX SoupTCP 1.0 test
      Add 'MbtMessage#updated(Any)'
      mbtrading/quoteapi: Handle messages without fields

Pekka Enberg (6):
      Merge pull request #148 from valotrading/releases/1.6.0
      Merge pull request #149 from jvirtanen/features/netstring
      Merge pull request #150 from jvirtanen/features/mbt-message-updated-any
      Oslo Børs Millennium Exchange ITCH 2.0
      Merge pull request #119 from valotrading/features/oslo-millenium-itch
      Merge pull request #151 from jvirtanen/fixes/mbt-quote-api-messages-without-fields
```