Add charset parameter to web.Response constructor

[asvetlov]

Existing content_type param is for type only, e.g. text/html or application/json.
Charset utf-8 is added ultimately and text is encoded as utf-8.

We need add charset param to constructor (urf-8 by default) and respect the param on text encoding.

Check for content_type should be added also to forbid ; (mark for charset) in the value.

The patch is trivial but should be proposed with tests.

Any volunteers for making Pull Request?

[asvetlov]

See also aio-libs/aiohttp-debugtoolbar#28

[jashandeep-sohi]

I have some free time this week. I'll take a crack at it.

[asvetlov]

Fixed. Thanks, @jashandeep-sohi

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