Added README describing hardware revisions

hardware/README.md

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+#### Hardware Revisions
+
+Most hardware that has been built has a version number
+
+|Version|Description|Exists/Existed|Flights used on
+|----|----|----
+|v0.96.0|Original AAA Battery. Flown with modifications to connect tcxo to mcu.|x|UBSEDS3-8?
+|v0.981.0|Solar Power SPV1040. Flown with modifications simplify power circuit.|x|UBSEDS9
+|v0.981.1|Minor fixes|
+|v0.982.0|AAA Battery. Never fully populated, used for lab testing.|x|
+|v0.982.1|Minor fixes|
+|v0.984.0|First attempt at internal balloon board|
+|v0.985.0|Solar Power/Primary AAA Lithium|