Using secure block cipher mode

[jlovison]

So I initially was only editing the random mode to the pyCrypto Crypto.Random.random method, when I noticed that the pycrypto defaults to ECB mode, which is sort of bad (I opened issue #27 which explains in a bit more detail why)

Rather than just offer a problem and not a solution, I edited the library to support better block cipher modes while retaining backwards compatibility, by allowing a field attribute block_type to be set, and using the better block ciphers only if that is set.

I also added a bit to the tests to test that this does in fact work as intended, and all existing tests pass.

I'd highly recommend a roadmap that eventually phases out the old behavior and makes the CBC mode default, but I figured invalidating everyone's data abruptly was a bad way to go about it.

Previous request:
The pyCrypto library includes a random method that's supposedly more "cryptographically secure" than the python random library.

I updated the imports to use this library instead of the python one.

[bltravis]

So, has this project been abandoned, or are these pull requests just being ignored?

[svetlyak40wt]

@bltravis I have no time to support it, but I can add you to this project's contributors, so you'll be able to push and merge pull requests. Do you want to become a project maintainer?

[bltravis]

Sure.

[svetlyak40wt]

Done

[bltravis]

Ok, I've already merged these changes into my fork, so they're rolled into pull request #24. I'm going to close this one and merge #24, which will kill two birds with one stone.