PyJulia does not work with Julia 1.0 & 0.7 with Python installed via Conda/Ubuntu/(what else?)

I'm writing down the issue so that it is easy to find by the users.

At the moment, for PyJulia to load Julia >= 0.7, two conditions have to be met:

1. Python interpreter configured for PyCall.jl and Python interpreter used to import PyJulia have to use identical `libpython` (once #190 is merged) have *exactly* identical paths.

2. The Python interpreter have to be dynamically linked (which is usually the case in Windows and macOS according to [this comment](https://github.com/JuliaPy/pyjulia/blob/25ab71cdc4fd17ef78127f3dd6e485d3efb8c327/julia/core.py#L246))

To check if condition 2 is the case, run:

```console
$ ldd /usr/bin/python | grep libpython
libpython3.7m.so.1.0 => /usr/lib/libpython3.7m.so.1.0 (0x00007f17c12c4000)
```

where `/usr/bin/python` is the appropriate Python interpreter.

If it does not print anything, you can't use PyJulia with this Python interpreter.