Merge pull request #528 from citibeth/efischer/160309-Emacs

Added Emacs package

var/spack/repos/builtin/packages/emacs/package.py

+from spack import *
+
+class Emacs(Package):
+    """The Emacs programmable text editor."""
+    homepage = "https://www.gnu.org/software/emacs"
+    url      = "http://ftp.gnu.org/gnu/emacs/emacs-24.5.tar.gz"
+
+    version('24.5', 'd74b597503a68105e61b5b9f6d065b44')
+
+    depends_on('ncurses')
+    # Emacs also depends on:
+    #     GTK or other widget library
+    #     libtiff, png, etc.
+    # For now, we assume the system provides all that stuff.
+
+    def install(self, spec, prefix):
+        configure('--prefix=%s' % prefix)
+        make()
+        make("install")