reword README files to list macOS as operating system

Author: jayponder

0README

@@ -17,7 +17,7 @@
          groovy, Mesa and Sun JCE routines.
 
          The /build directory has a build environment for constructing
-         FFE install kits for Linux, MacOS and Windows. Scripts provided
+         FFE install kits for Linux, macOS and Windows. Scripts provided
          allowing building of FFE installers via the install4j program.
          See /build/0README for the exact procedure for building full
          Tinker-FFE installer kits.

README.md

@@ -2,7 +2,7 @@
 
 <H2><B>Introduction</B></H2>
 
-The Tinker-FFE ("Force Field Explorer") software is a Java-based GUI for molecular design and engineering, originally written by Prof. Michael J. Schnieders, now in the Department of Biomedical Engineering at the University of Iowa. In addition to a variety of general molecular modeling and visualization capabilities, Tinker-FFE enables launch and control of Tinker calculations from an easy-to-use graphical interface. Molecular and biomolecular structures can be downloaded from the PubChem, NCI and PDB databases. The Tinker-FFE package runs on Linux, Macintosh and Windows systems.
+The Tinker-FFE ("Force Field Explorer") software is a Java-based GUI for molecular design and engineering, originally written by Prof. Michael J. Schnieders, now in the Department of Biomedical Engineering at the University of Iowa. In addition to a variety of general molecular modeling and visualization capabilities, Tinker-FFE enables launch and control of Tinker calculations from an easy-to-use graphical interface. Molecular and biomolecular structures can be downloaded from the PubChem, NCI and PDB databases. The Tinker-FFE package runs on Linux, macOS and Windows systems.
 
 <H2><B>Installation Kits</B></H2>