Added code to detect assembler directives and did some minor code clean up.

misc/test.asm

@@ -1,12 +1,13 @@
 ; comments are ignored
 ; This is a very simple test file for an assemblier.
-.db msg "Hello, world!"
+.org 0x100
+.db msg "Hello, world!", 0
 
 copy r1, msg
 copy r2, 0
-.loop:
+loop:
     cmp r1, 0
-    jz .loop
+    jz loop
     add r1, 1
 mov r1, 5   ; move the immediate value 5 into r1
 add r1,5   ; add 5 into r1