Merge pull request #4 from DanielaIvanova/hex-release

Added necessary information for hex release

rebar.config

@@ -0,0 +1 @@
+{plugins, [rebar3_hex]}.

src/base58.app.src

@@ -7,5 +7,5 @@
                   kernel,
                   stdlib
                  ]},
-  {env, []}
+  {licenses, ["Apache-2.0"]},
- ]}.
+  {links, [{"GitHub", "https://github.com/aeternity/erl-base58"}]}]}.