adds first version of the expanded as assembler from mikko

lib/asm/README.markdown

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+Assembler in Ruby
+=================
+
+Supporting arm, but aimed quite specifically at raspberry pi, arm v7, floating point included
+
+Outputs ELF object files, with relocation support.
+
+Constant table support exists but isn't very good. Some addressing modes
+are not supported or only partially supported.
+
+Supported (pseudo)instructions:
+
+- adc, add, and, bic, eor, orr, rsb, rsc, sbc, sub, cmn, cmp, teq, tst,
+  mov, mvn, strb, str, ldrb, ldr, push, pop, b, bl, bx, swi
+- Conditional versions of above
+
+Thanks to Cyndis for starting this arm/elf project in the first place: https://github.com/cyndis/as
+