Remove required_otp_version
Maintaining this may be more trouble than it's worth, so rather than
keep updating, let's try removing this line, and address any problems
as they arise.
diff --git a/rebar.config b/rebar.config
index 3b93f8a..cfc4d73 100644
--- a/rebar.config
+++ b/rebar.config
@@ -1,5 +1,3 @@
-{require_otp_vsn, "R14|R15|R16|17|18|19|20|21|22|23|24|25"}.
-
{erl_opts, [debug_info, warn_unused_vars, warn_shadow_vars, warn_unused_import]}.
{port_sources, ["c_src/*.cc",
"c_src/snappy/*.cc"]}.
