v0.6.6

Minor release.

New features:

• Native trailing stops - available for strategies (@askmike - #2429). Read the details here: https://forum.gekko.wizb.it/thread-57314-post-60075.html#pid60075

Minor changes:

• [GB] Use forked Poloniex dependency (@askmike - #2433, #2435)
• [DOCS] Improve feature docs (@askmike - #2436)
• [GB] Handle inconsistent CoinFalcon response regarding open orders (@askmike - #2441)
• [CLI] Improve roundtrip formatting (@GuysmoB - #2447)
• [GB] Better handle partial fills on binance (@askmike - #2450)
• [UI] Improve the websocket server error handling (@askmike - #2462)
• [GB] Log a user friendly error on missing GB deps (@askmike - #2464)
• [CORE] Improve child process exit (@eusorov - #2467)
• [CORE] Stop the candleLoader after failing to load more candles (#2475 - @eusorov)