Python 3 Support

[pipermerriam]

What was wrong?

• Travis CI is not enabled
• There was a print statement that isn't python 3 compatable.
• The market.se contract needed to be updated to the new extern format (see compilation error on cyberdyne market example #85)
• The package didn't specify anything about what versions of python it is compatable with.
• No python3 support.
• The README was very sparse in general information about the package.

How was it fixed?

• Added a basic .travis.yml and tox.ini file.
• Converted the print statement to be python3 compatable.
• Redid the extern statements to be correct.
• Added classifiers for python 2.7/3.4/3.5
• Added info to the README on how to run the tests.

Cute animal picture

[pipermerriam]

This PR should resolve the following issues.

• Python 3 support #94 - Python 3 compatability.
• compilation error on cyberdyne market example #85 - compile error on the market.se example contract.

[pipermerriam]

@vbuterin could you take a look at this? Potentially enable travis-ci on this repo and let me know what's needed to get this merged.

[PiDelport]

These basepython declarations shouldn't be needed anymore for non-ancient versions of Tox.

[pipermerriam]

Neat, I didn't know that. fixed.

[pipermerriam]

@tgerring I was told that you might be able to enable travis-ci for this repository? Also, looking for someone who has merge permissions. I got the 👍 from @vbuterin over skype.

I'd like to see tests passing on travis prior to merging though.

[tgerring]

@pipermerriam The ethereum/serpent repo has been activated on Travis

[pipermerriam]

ok, looks like the test failures are related to not having python3 in pyethereum. I'm going to deal with this on the pyethereum side and then we'll get this merged.

[pipermerriam]

Just noting that the tests for this pass when run against the pyethereum branch with python 3 support. See #103