Is it possible to set up a custom domain with GitHub Pages, but keep the original github.io link working without redirection?

Question

Is there any way I can set up a custom domain with GitHub Pages (e.g. www.vinyanalista.com.br), but also keep the original github.io link working (e.g. vinyanalista.github.io)? That way, my website could be accessed by both addresses (www.vinyanalista.com.br or vinyanalista.github.io) without redirection.

Now, what is happening is:

• http://vinyanalista.github.io (my GitHub user page) is automatically redirected to http://www.vinyanalista.com.br (my custom domain)
• http://vinyanalista.github.io/blog/2015/06/24/favicon/ (a post of my blog) is automatically redirected to http://www.vinyanalista.com.br/blog/2015/06/24/favicon/
• http://vinyanalista.github.io/portugol (a website for a project of mine) is automatically redirected to http://www.vinyanalista.com.br/portugol

The setting I want is:

• http://vinyanalista.github.io can be accessed without redirection (i.e. the URL in the address bar does not change)
• http://www.vinyanalista.com.br can be accessed without redirection
• http://vinyanalista.github.io/blog/2015/06/24/favicon/ can be accessed without redirection
• http://www.vinyanalista.com.br/blog/2015/06/24/favicon/ can be accessed without redirection
• http://vinyanalista.github.io/portugol can be accessed without redirection
• http://www.vinyanalista.com.br/portugol can be accessed without redirection (although I don't really mind this use case, because I want http://vinyanalista.github.io/portugol to be accessed that way, as it was before I set up www.vinyanalista.com.br as a custom domain for vinyanalista.github.io)

Thanks in advice!

Edit: my DNS setup right now is:

Host    -        IP/Address
@       A        192.30.252.153
@       MX 5     ASPMX.L.GOOGLE.COM.
@       MX 10    ALT1.ASPMX.L.GOOGLE.COM.
@       MX 15    ALT2.ASPMX.L.GOOGLE.COM.
@       MX 20    ASPMX2.GOOGLEMAIL.COM.
@       MX 25    ASPMX3.GOOGLEMAIL.COM.
@       A        192.30.252.154
mail    CNAME    ghs.google.com.
www     CNAME    vinyanalista.github.io.