Implement _encode_entity for Python 2.7

[mnaberez]

Pull request #4 fixed a bug where _encode_entity was used by the code but not being imported.

On Python 2.7, this method was removed (we also had this problem with fixtag). The patch in #4 defines it as a no-op but we should put in an actual implementation.

[puentesarrin]

Can I port the code from 2.5/2.6 and send the pull-request?

[mnaberez]

Absolutely. Thanks!

[mnaberez]

I tweaked this a little in 0738881 to remove the check for Python 1.5, since meld3 doesn't work on that version.

It's unfortunate that the tests did not catch the problem you originally reported in #4. Do you have some sample input that we can add to test_meld3.py to make sure we don't break it again?

[puentesarrin]

Simply test with any character with accent, such as: "á" or "é".

[puentesarrin]

Excelent! @mnaberez thanks for merge.