Replace '\n' with os.EOL and add consistency for last new line

[obenjiro]

Let's avoid using platform specific constants directly. And new need to output last new line consistently across the app

[bardware]

First thing I noticed; inserted line breaks are new line instead of 0D0A

[obenjiro]

Done partially. We need to detect "line-end" for CSS file and use it instead. Will be done in separate issue

[bardware]

Will be done in separate issue

I just found this issue addressing the new lines: #367

[obenjiro]

@bardware tnx, even more reason to close, since it's duplicate. I fixed output for terminal, but all other places require extra work. Will do that when I got an idea how to handle it. It will be fixed in #367