Convert README to rst for upload to PyPI

[jaseg]

Since I needed pcb-tools as a dependency for one of my projects I quickly uploaded it to PyPI. To make the README work with PyPI I had to convert it to restructuredtext and replace all included images with absolute external links, since PyPI doesn't seem to be able to reference images from within the uploaded egg.

I'll happily transfer the PyPI project to you if you want to maintain it yourself, in that case please just send me your pypi username.

[coveralls]

Coverage remained the same at 81.067% when pulling 48ee76a on jaseg:pypi into 256cd7e on curtacircuitos:master.

[phsilva]

Thanks @jaseg. If you could, please transfer it phsilvaon PyPI. I will rebase this changes and merge it today.

[phsilva]

Think we could just use long_description_content_type='text/markdown' and upload a new version to PyPI. As soon as you transfer I will upload a new version.

[jaseg]

You should have "owner" access to the package now. If everything works, you can remove me from the package.

[phsilva]

You should have "owner" access to the package now. If everything works, you can remove me from the package.

Thanks @jaseg!