Deprecated installation instructions

**Describe the bug**
Following the installation instructions in the README results in an error.

**To Reproduce**
Follow the installation instructions including the line

```bash
> python setup.py install
```

**Expected behavior**
The package should be correctly installed.

**Output**
```bash
> (python: can't open file '/home/cyberguli/PyGeM/setup.py': [Errno 2] No such file or directory)
```


