Ship librtmp.dll on Windows

[techtonik]

>>> import librtmp
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\librtmp\__init__.py", line 8, in <module>
    from ._librtmp import ffi, lib as librtmp
ImportError: DLL load failed: The specified module could not be found.
>>>

_librtmp.pyd is there, but it requires librtmp.dll, which is nowhere to be found.

[okskmk2]

same issue here.

[wilsonssss]

resolution: #35 (comment)