added README for new users

README.md

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+
+# 4 variable boolean simplifier
+
+Boolean simplifier uses brute-force to generate all simplest expression trees
+for any 4-variable truthtable. It's pretty cool! And it has a repl! and it has
+colors! It uses dynamic programming to run in reasonable time.
+
+The python script takes 6 hours, the C program takes 30 seconds.
+
+By default, the program will simplify/re-write the given expression(s) using
+only "or", "and" and "not" operators. You can tell it to use all supported
+operators ("xor", "xnor", "nor", "nand", etc.) using `-e`. Or, you can
+explicitly control which operators to use using `-o`. Ternary takes a long
+time, so it is not included in `-e`, you have to speficially request it using
+`-o`. Out of the box, it'll have to build it's cache, you can use `-B` to
+force a rebuild.
+
+