add cygwin support

[ognevny]

fixes #353

[mmastrac]

I don't have a good environment set up to test this - do the examples succeed? Merged as-is for now, will release shortly as 0.6.2

[ognevny]

I don't have a good environment set up to test this - do the examples succeed? Merged as-is for now, will release shortly as 0.6.2

example succeeded. other depends on libloading, which isn't supported for cygwin itself

edit: you can setup MSYS2 environment and use MSYS shell

[mmastrac]

Released as 0.6.2, thanks!