Prior version was "2". New functional tests suite
was not being picked up by local rebar, but was
execute with my local which is version "2.5.2"
which targets the same version of Erlang/OTP
as iBrowse (R16).

* Add rebar
* Move build flags from src/Makefile to rebar.config
* Remove src/Makefile
* Put version in src/ibrowse.app.src
* Remove vsn.mk
* Remove ebin/ibrowse.app
* Change Makefile to read version from src/ibrowse.app.src
* Change Makefile all target to call ./rebar compile
* Change Makefile clean target to call ./rebar clean
* Update .gitignore to ignore ebin/*