Updated gfortran version dependency tree documentation

doc/dependency_tree/opencoarrays-tree.txt contains the output of "tree opencoarrays" and provides a static depiction of the dependency tree. The installation script prints this file in its initial output.  This commit updates the listed gfortran version to 5.3.0.

Author: Damian Rouson

doc/dependency_tree/opencoarrays-tree.txt

@@ -1,7 +1,7 @@
 opencoarrays
 ├── cmake-3.4.0
 └── mpich-3.1.4
-    └── gcc-5.1.0
+    └── gcc-5.3.0
         ├── flex-2.6.0
         │   └── bison-3.0.4
         │       └── m4-1.4.17