Update README with features and examples

README.md

@@ -1,5 +1,48 @@
 # VerifiableStatementCompiler
 
-libsnark has to be installed to: `lib/libsnark`
+## Using VerifiableStatementCompiler
 
-`export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib`
+Set include the libsnark library path in `LD_LIBRARY_PATH`
+```
+export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
+```
+
+Command
+```
+./code_to_r1cs program [inputs]
+```
+- `program`: Path to the program that you want to be compiled.
+- `inputs` (optional): String of variable assignments of the inputs of a program split with whitespaces.<br>
+
+### Example
+
+To execute the program
+```
+def add(a, b, c):
+  return a + b + c
+```
+with `add(1, 2, 3)`, call
+```
+./code_to_r1cs program "1 2 3"
+```
+
+## Building
+
+Currently needs to be build with nightly Rust.
+
+### With libsnark
+
+Install [libsnark](https://github.com/scipr-lab/libsnark) to `/usr/local` with
+```
+make install lib PREFIX=/usr/local NO_PROCPS=1 NO_GTEST=1 NO_DOCS=1 CURVE=ALT_BN128 FEATUREFLAGS="-DBINARY_OUTPUT=1 -DMONTGOMERY_OUTPUT=1 -DNO_PT_COMPRESSION=1"
+```
+and build with
+```
+cargo build
+```
+
+### Without libsnark
+Build with the feature `nolibsnark`
+```
+cargo build --features nolibsnark
+```