Postpone some imports
Bypass proxy when needed

This urllib function is not well documented, but should do reasonably
well on OSX and Windows. On Linux it won't work with something like
http://localhost:55555 (which is what localtm uses).
Use libproxy if available

This should vastly improve our ability to work with proxies on Linux,
especially when proxy settings change while Virtaal is running. We
might even support PAC now! In theory this might work on other platforms,
but only Linux is tested, and Linux seems to be the main target for
libproxy. Our proxy support on Windows and OSX should be much better
simply because urllib provides us with more on those platforms.
Document libproxy as optional dependency
Update with newest from Microsoft

Some missing codes were now filled in from ISO tables.
Typo
Some extras for vim