Upgrade to Babel 7

[kpman]

No description provided.

[tw0517tw]

I thought there is a babel issue blocking this.
babel/babel#8280

[codecov-io]

Codecov Report

Merging #300 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #300   +/-   ##
=======================================
  Coverage   90.27%   90.27%           
=======================================
  Files         112      112           
  Lines        3291     3291           
  Branches      779      779           
=======================================
  Hits         2971     2971           
  Misses        280      280           
  Partials       40       40

Impacted Files	Coverage Δ
src/context/TelegramContext.js	70.37% <ø> (ø)	⬆️
src/bot/ConsoleConnector.js	100% <ø> (ø)	⬆️
src/context/Context.js	100% <ø> (ø)	⬆️
src/bot/TelegramBot.js	100% <ø> (ø)	⬆️
src/context/ConsoleContext.js	100% <ø> (ø)	⬆️
src/context/LineContext.js	99.06% <ø> (ø)	⬆️
src/context/TelegramEvent.js	100% <ø> (ø)	⬆️
src/context/SlackContext.js	90.47% <ø> (ø)	⬆️
src/bot/ViberConnector.js	90.32% <ø> (ø)	⬆️
src/bot/TestConnector.js	100% <ø> (ø)	⬆️
... and 11 more

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