hexdump for binary diffs

those with an existing repo should run:

git config diff.hex.textconv hexdump

.gitattributes

@@ -1,2 +1,12 @@
 # No monkey business with line endings
 * -text
+
+# hexdump binary files
+*.png  diff=hex
+*.lz   diff=hex
+*.2bpp diff=hex
+*.1bpp diff=hex
+*.pal  diff=hex
+*.bin  diff=hex
+*.blk  diff=hex
+

INSTALL.md

@@ -41,6 +41,9 @@ cd pokecrystal
 
 # install python requirements
 pip install -r requirements.txt
+
+# use hexdump to diff binary files
+git config diff.hex.textconv hexdump
 ```
 
 To compile the ROM from ASM source: