Use /bin/sh; quote shell variables (#46)

* On macOS, sh is /bin/sh not /usr/bin/sh

* Quote shell variables correctly

README.md

@@ -90,9 +90,9 @@ or create a shell script (in `/usr/local/bin`, etc)
 
 `/usr/local/bin/AsmIIgs`:
 
-    #!/usr/bin/sh
+    #!/bin/sh
     
-    exec mpw AsmIIgs $@
+    exec mpw AsmIIgs "$@"
 
 
 mpw uses the MPW `$Commands` variable to find the command, similar to `$PATH` on Unix.  If the `$Commands` variable

README.text

@@ -84,9 +84,9 @@ or create a shell script (in /usr/local/bin, etc)
 
 /usr/local/bin/AsmIIgs:
 
-#!/usr/bin/sh
+#!/bin/sh
 
-exec mpw AsmIIgs $@
+exec mpw AsmIIgs "$@"
 
 mpw looks in the current directory and then in the $MPW:Tools: directory
 for the command to run.  The MPW $Commands variable is not yet supported.

verbatim/makefile.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/sh
+#!/bin/sh
 
 infile="$1"