add compilation guide on windows

[zoowii]

I add a guide to build electrum on pure-Windows environment, without usage of Wine

[coveralls]

Coverage remained the same at 42.916% when pulling fdf2bd8 on zoowii:master into dc388d4 on spesmilo:master.

[coveralls]

Coverage remained the same at 42.916% when pulling 8ce5ee8 on zoowii:master into dc388d4 on spesmilo:master.

[bauerj]

Hey,

thanks for this guide. We don't use Windows to build the binaries so we can't say whether this is correct or not. Furthermore, we will not be able to update this guide with future changes as that would require too much time for testing.

However, since this seems to be useful for anyone wanting to build it on Windows, you can consider to add this to the community wiki here on Github if you add a disclaimer that this is not officially supported.