Update README.md

Expand documentation with risks and status.
Include a local rebar3 build to include erlang/rebar3#2863.
Extend commands to use path environment variable to prevent erlang/otp header mismatch.

README.md

@@ -1,19 +1,36 @@
 ## BeamQN
 
-An experiment in linking [CBQN](https://github.com/dzaima/CBQN) into the Erlang BEAM as a NIF. 
+An experiment in linking [CBQN](https://github.com/dzaima/CBQN) into the Erlang BEAM as a NIF.
+
+### Status
+
+BeamQN is experimental software and is **not ready for production use**. Use at your own risk!
+
+The risks of using this library include, but are not limited to:
+* Memory leaks
+* Scheduler collapse
+* Undefined behavior
+* System crash
+
+In order to rapidly identify bugs, it is recommended to develop BeamQN applications using a debug enabled Erlang runtime system.
+A general guide for building a debug enabled Erlang runtime system and the latest Rebar3 build tool is below.
 
 ### Build (Development)
 
 1. Download and extract the latest Erlang/OTP release tarball from the [downloads page](https://www.erlang.org/downloads).
 2. Export `$ERL_TOP` to the path of the extracted source.
 3. [Build Erlang/OTP from the release tarball.](https://www.erlang.org/doc/installation_guide/install#how-to-build-and-install-erlang-otp)
 4. [Build the debug enabled runtime system.](https://www.erlang.org/doc/installation_guide/install#Advanced-configuration-and-build-of-ErlangOTP_Building_How-to-Build-a-Debug-Enabled-Erlang-RunTime-System)
-5. Using the compiled runtime for development:
+6. [Install Rebar3 from source using the latest Erlang/OTP release tarball.](https://rebar3.org/docs/getting-started/#installing-from-source)
+```
+env PATH=$ERL_TOP:$PATH ./bootstrap
+```
+7. Export `$REBAR_TOP` to the path of the rebar3 source.
+8. Using the compiled runtime for development:
 
    #### Debug
-
-       $ PATH="$ERL_TOP/bin:$PATH" rebar3 compile
-       $ PATH="$ERL_TOP/bin:$PATH" cerl -debug +pc unicode -pa ebin -pa ./_build/default/lib/*/ebin
+       $ env PATH=$ERL_TOP/bin:$PATH $REBAR_TOP/rebar3 compile
+       $ env PATH=$ERL_TOP/bin:$PATH cerl -debug +pc unicode -pa ebin -pa ./_build/default/lib/*/ebin
 
 ### Installation (Erlang)
 
@@ -41,13 +58,13 @@ end
 
 Documentation can be generated with [EDoc](https://www.erlang.org/doc/man/edoc).
 ```
-rebar3 edoc
+env PATH=$ERL_TOP/bin:$PATH $REBAR_TOP/rebar3 edoc
 ```
 Once generated, the docs can be found at `/doc/`.
 
 ### Testing
 
 Tests can be ran with [EUnit](https://www.erlang.org/doc/apps/eunit/).
 ```
-rebar3 eunit
+env PATH=$ERL_TOP/bin:$PATH $REBAR_TOP/rebar3 eunit
 ```