Requirements for pull request

[ramezquitao]

I just wrote a simple plugin, taking as example the bz2 plugin and included in it the LZO code from pytables. For my application what I did is enough, but I would like to contribute this small piece of code to the External Filters Plugins. Are there any requirements about the code or some standards I should follow so the LZO plugin can be included? For example, I deleted all the tests, but I dont know if you require some tests or not.