STYLE: Improve the README.rst file style.

Improve the `README.rst` file style, and conform to `ITKModuleTemplate`
conventions:
- Divide the file into sections.
- Cross-reference the `LICENSE` file.
- Improve the IJ citation to conform to common format.

Author: jhlegarreta

README.rst

@@ -16,20 +16,36 @@ ITKMinimalPathExtraction
 |CircleCI|  |TravisCI|  |AppVeyor|
 =========== =========== ===========
 
+
+Overview
+--------
+
 This is an `ITK <http://itk.org>`_ module that implements a minimal path
 extraction framework based on Fast Marching arrival functions.
 
 A more detailed description can be found in
 `the Insight Journal article <http://hdl.handle.net/1926/1332>`_::
 
-  Mueller, D. "Fast Marching Minimal Path Extraction in ITK"
+  Mueller, D.
+  "Fast Marching Minimal Path Extraction in ITK"
+  The Insight Journal. January-June, 2008.
   http://hdl.handle.net/1926/1332
   http://www.insight-journal.org/browse/publication/213
-  March, 2008.
 
-Since ITK 4.8.0, this module is available in the ITK source tree as a Remote
-module.  To enable it, set::
+
+Installation
+------------
+
+Since ITK 4.8.0, this module is available in the ITK source tree as a remote
+module. To enable it, set::
 
   Module_MinimalPathExtraction:BOOL=ON
 
 in ITK's CMake build configuration.
+
+
+License
+-------
+
+This software is distributed under the Apache 2.0 license. Please see
+the *LICENSE* file for details.