Improve 2015/howe/try.sh and fix make clobber

The make clobber rule now removes *.tmp instead of just specific .tmp
files.

Updated .gitignore: removed the foo.tmp globs and added *.tmp.

2015/howe/Makefile

@@ -214,7 +214,7 @@ clean:
 clobber: clean
 	${RM} -f ${TARGET} ${ALT_TARGET}
 	${RM} -rf *.dSYM
-	${RM} -f curds.tmp nuked.tmp whey.tmp makeholes
+	${RM} -f makeholes *.tmp
 	@-if [ -e sandwich ]; then \
 	    ${RM} -f sandwich; \
 	    echo 'ate sandwich'; \