describe the installation in more detail

README

@@ -1,8 +1,20 @@
 * Install
 Install in "development mode" so any change of the program is effective.
-pip install -e .
+
+Note: For system wide (global) installation log in as root or use sudo for example.
+For local (user) installation the local path must be in the PYTHONPATH environment variable.
+Typically $HOME/.local/lib/pythonX.Y/site-packages
+
+' pip install -e .
 or
-python -m pip install -e .
+' pip install --user -e .
+or
+' python -m pip install -e .
+or
+' easy_install --prefix=$HOME/.local -e .
+or
+' pip install --install-option="--prefix-$HOME/.local" -e .
+
 
 * Uninstall
 pip uninstall materials