Add README file

Add `README.md`, which contains an overview of the content of this
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README.md

+# Paper artifacts
+
+This repository contains the artifacts produced for the *Performance, Correctness, Exceptions: Pick Three* paper, part of the 2019 BAR workshop.
+
+This repository contains:
+
+- A `Getting-Started` file, which contains the instructions for reproducing from scratch the results (building *rev.ng*, translating the binaries and running the *SPEC* benchmarks).
+- A `results` folder which contains the data collected and used for the results presented in the paper (it contains both a `raw-results` sub-folder, which contains the raw data produced during the *SPEC* runs, and the `aggregated-paper-results` sub-folder, which contains the data used for the results presented in the paper).
+- A `binaries` folder, which contains the binaries used during the benchmarks. In particular, the `native` sub-folder contains the binaries as they are built by *SPEC*, the `revamb` sub-folder contains the binaries translated by *rev.ng*, and the `revambisolated` sub-folder contains the binaries translated by *rev.ng*, with the additional function isolation pass.
+All the results are provided in an archive which is commited in the repository using `git-lfs`.