Fix for #177 still appears broken for frozen apps

[jwiggins]

The relevant PyInstaller issue is here: pyinstaller/pyinstaller#3407

I believe the original suggestion in #177 to skip the find_library checks in https://github.com/PyTables/PyTables/blob/develop/tables/__init__.py#L26-L86 would be better for frozen apps. Ideally, testing on an un-frozen version should have already established that the HDF5 library is correctly installed.

PyInstaller is doing some monkey patching which interacts badly with PyTables, which I pointed out in the above linked issue. Again, just skipping the check when sys.frozen is True would bypass the problem.

[tomkooij]

@jwiggins : Let's just fix this. Can you provide a PR with that original fix from #177 implemented (again)? LGTM.

[jwiggins]

@tomkooij Done!