Gentoo/Pentoo/Sabayon install

Added validation for Gentoo
```if os.path.isfile("/etc/portage/make.conf"):```

Prereqs to install
```subprocess.Popen("emerge pexpect imaging pycrypto pyopenssl && wget https://pefile.googlecode.com/files/pefile-1.2.10-139.tar.gz && tar xvfz pefile-1.2.10-139.tar.gz && chmod a+x pefile-1.2.10-139/setup.py", shell=True).wait()```

Cleaned up some whitespace and fixed a spelling error.