Fixed the platform detection for 32-Bits or 64-Bits

| Q               | A
| --------------- | ---
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Tests pass?     | yes
| Related tickets | #26, #33
| License         | GNU GPLv3

- [x] Added a test for detecting the right architecture
- [x] Running test under Windows 64 bits platform

If running `cyg-apt` on Windows 64 bits and with a python 64 bits then It is not an obligation that the Cygwin platform is also on 64-bit. To avoid that indecision maybe we should add an `architecture` configuration field for the version 1.2.

However I was not successfully used `cyg-apt` outside Cygwin, I'll try try again. This is another issue but this issue need it. Moreover I cannot tests it on 64 bits architecture.

So for the moments we cannot say it works for 64 bits architecture without an efficient test suite.

From #26:
> This PR implements most of the functionality described in #8, except for an option to set the package architecture, which should not be needed.