Replaced all instances of 'python' with 'python2'

On systems where 'python' refers to python3, redo
failed to launch. All invocations of python have been
made explicitly python2 invocations. All tests pass
on an Arch Linux system as of this commit.

install.do

@@ -26,7 +26,7 @@ for d in *.py version/*.py; do
 	fix=$(echo $d | sed 's,-,_,g')
 	$INSTALL -m 0644 $d $LIBDIR/$fix
 done
-python -mcompileall $LIBDIR
+python2 -mcompileall $LIBDIR
 
 # It's important for the file to actually be named 'sh'.  Some shells (like
 # bash and zsh) only go into POSIX-compatible mode if they have that name.
@@ -37,7 +37,7 @@ for dd in redo*.py; do
 	d=$(basename $dd .py)
 	fix=$(echo $d | sed -e 's,-,_,g')
 	cat >install.wrapper <<-EOF
-		#!/usr/bin/python
+		#!/usr/bin/python2
 		import sys, os;
 		exedir = os.path.dirname(os.path.realpath(os.path.abspath(sys.argv[0])))
 		sys.path.insert(0, os.path.join(exedir, '../lib/redo'))