LH: I have fixed issues in the PR and incorporated changes
from a sister PR by @djankovic (git author: Dom J). I also
made sure the UTF-8 files were readable without Chinese
fonts and added their downloading to the examples test suite.
They are now cowboy:start_clear/3 and cowboy:start_tls/3.
The NumAcceptors argument can be specified via the
num_acceptor transport option. Ranch has been updated
to 1.4.0 to that effect.
The new example is called file_server and it's basically
the same as web_server was. The name is clearer than the
original, all examples being "Web servers".
The new example is also tested and the test suite has
been refactored a little.
