kykint / TELEGRAMBOT

Previous way translate() determined its source and target language was inflexible and inconvenient.
For example a user always had to change target language according to whether he wants to translate
into other language or his own.

Improve this by assuming that user wants to translate his own language into other language when
source language matches the user's locale, and the opposite if it doesn't.

Also make some other improvements to logic:
- translate() now doesn't send a message to user directly, and instead returns a Promise.
- Also it takes a full user info instead of userId as a parameter, allowing it to detect
  user's locale as well.

WIP. Needs a way to save user's choice.

Usage: /l or /language

- Let user select the language he wants his message to translate to.
  When triggered, bot will send an inline keyboard message with a list
  of available langauges. For an example of an inline keyboard message,
  see https://core.telegram.org/bots#inline-keyboards-and-on-the-fly-updating.

Usage: /t [Whatever]
       or /translate [Whatever]

- Translate the 'whatever' and show the result in any kind of chatroom.
  Also, if the given '/t' message is a reply to another message,
  translate the reply target message as well.

Otherwise it would reply to every single message on e.g. group chats.

Server can now be executed with `npm start`.