message: chore CHANGELOG for v0.27.0
diff: +# [v0.27.0](https://github.com/nervosnetwork/ckb/compare/v0.26.1...v0.27.0) (2020-01-10)
  +
  +### Features
  +
  +* #1882: Add tcp and websocket to rpc service (@quake). This is required for #1867.
  +* #1890 **spec:** Configurable block bytes limit (@zhangsoledad)
  +
  + Provide `max_block_bytes` option supports configurable block bytes limit.
  +
  +* #1891: Notify service (@quake)
  +
  + This PR resolve #1860 and refactor network alert script notification by adding a notify service, and it's required to implement #1867.
  +
  + **configuration file breaking change**
  +
  + ```diff
  + -# [alert_notifier]
  + -# # Script will be notified when node received an alert, first arg is alert message string.
  + -# notify_script = "echo"
  + +# [notifier]
  + +# # Execute command when the new tip block changes, first arg is block struct in json format string.
  + +# new_block_notify_script = "your_new_block_notify_script.sh"
  + +# # Execute command when node received an network alert, first arg is alert message string.
  + +# network_alert_notify_script = "your_network_alert_notify_script.sh"
  + ```
  +### Bug Fixes
  +
  +* #1889: `get_cell_meta` should return None if output index does not exist (@jjyr)
  +* #1895: Fix peer store saving failed due to temp dir does not exist (@jjyr)
  +* #1899 **tests:** Rpc server should explicit close (@zhangsoledad)
  +
  +### Improvements
  +
  +* #1894: Reduce useless clone / to_owned use (@driftluo)
  +
  + Reduce useless clone / to_owned use
  +
  # [v0.26.1](https://github.com/nervosnetwork/ckb/compare/v0.26.0...v0.26.1) (2019-12-30)
  ### Features
  