Improved README: added clarification example for MPI dependencies

README.md

@@ -1,11 +1,15 @@
-Software Installation Tool (SIT)
---------------------------------
+# Software Installation Tool (SIT)
 
+## About
 SIT is a simple software installation tool inspired by gentoo's emerge script.
 It eases the installation process and helps to prevent errors during the
 installation as well as helps with the documentation as it generates a lot of
 log files and installes them together with the softwre package.
 
+## Getting started
+
+### Basic usage
+
 In its current version it can only install a package using a package class file
 including the necessary information
 
@@ -19,7 +23,6 @@ It includes a variety of default values:
 * PREFIX_BASE
 * SRC_POOL
 * SCLASS_DIR
-
 * DEFAULT_PLATFORM
 * DEFAULT_COMPILER
 
@@ -39,7 +42,9 @@ Sit detects currently the build platform using the SITE_PLATFORM_NAME variable.
 If sit cannot determine the PLATFORM it uses the default platform specified
 in sit.conf.
 For each platform configuration files are stored unter
-  $SIT_PATH/etc/platform-configs/$PLATFORM/*
+```shell
+$SIT_PATH/etc/platform-configs/$PLATFORM/*
+```
 
 At the moment only compiler configurations are supported.
 
@@ -52,9 +57,11 @@ e.g.
 
 > PREFIX_BASE=/opt COMPILER=gnu COMPILER_VERSION=4.5 sit mpi/openmpi-1.5.1
 
+or for a package to be installed with a specific compiler and mpi version
 
+> PREFIX_BASE=/opt COMPILER=gnu COMPILER_VERSION=8.3.0 MPI=openmpi MPI_VERSION=4.0.1 ./sit performance/extrae/extrae-3.6.1
 
-PACKAGE FILES:
+### Package files
 
 Package files should include all the necessary information for the installation
 proces. The syntax of the package class files is inspired by gentoo's ebuild files.