Support twitter auth

[nbys]

To resolve #31

[coveralls]

Pull Request Test Coverage Report for Build 257

• 112 of 158 (70.89%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.2%) to 84.205%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
auth.go	0	2	0.0%
provider/oauth1.go	95	139	68.35%

Totals
Change from base Build 255:	-1.2%
Covered Lines:	1594
Relevant Lines:	1893

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💛 - Coveralls

[umputun]

very nice, thx!

From first glance, it looks good and clean, but I'll take a closer looks tonight (hopefully).

Have you tried to run it with the real twitter auth?

[nbys]

yeap, I tried to run _example/main.go with the real twitter application. It looks good.

There is one thing I am not sure about this implementation though. It is usage of State field of handshake. Basically there is no concept of state in oauth1. But there are request token and request secret. At first they are used for user authentication request. After redirection to callback url (if user authentication was successful) they are needed for access token request.
To me the purpose of requestSecret in oauth1 is somehow similar to state in oauth2: to check if after redirection it is still the same user that originated authentication process.

[nbys]

here requestSecret is set for later usage in AuthHandler

[umputun]

To me the purpose of requestSecret in oauth1 is somehow similar to state in oauth2

makes sense.