Dns resolve from code

[justcoding121]

Doneness:

• Build is okay - I made sure that this change is building successfully.
• No Bugs - I made sure that this change is working properly as expected. It doesn't have any bugs that you are aware of.
• Branching - If this is not a hotfix, I am making this request against master branch

[AppVeyorBot]

✅ Build Titanium-Web-Proxy 3.0.688 completed (commit 2b4dddbc19 by @justcoding121)

[gustyr]

I have an issue with this change when using an external proxy. Latest stable 3.0.684 was working fine.

https://github.com/justcoding121/Titanium-Web-Proxy/blob/bf983616ba51ece4ce7587a568760068e4e5b578/src/Titanium.Web.Proxy/Network/Tcp/TcpConnectionFactory.cs#L290

Dns.GetHostEntry(hostname) throws exception when using a proxy an upstreamproxy like "10.1.13.1:3128"
using GetHostAddresses no exception is thrown.

[justcoding121]

Should be fixed in latest beta.