Removed separate compilers
Resolves apps to build
Finds avail deps before pulling/building
Includes relx
Simplifies build commands

Fix OS X resource fork handling (Reported-by: Richard O'Keefe)

If you happen to fetch a zip archive of the git repo and try to build
from that, you may, for example, ask erlc to build src/._rebar.erl.
._* are OS X resource forks and not real .erl files. This may also
happen with network filesystems on OS X. To fix that, limit the
files compiled by rebar to include only those which start with
a letter or a digit.

Update dialyzer_reference

Remove experimental label from 'eunit tests='

Follow-up typo fixes for #327

Adapt arch string to versioning scheme changes (>= 17.x)

As mentioned in the OTP documentation, licensed customers may use
patched OTP installations where the otp_patch_apply tool adds a '**'
suffix as a flag saying the system consists of application versions from
multiple OTP versions. When we get such a version string, we drop the
suffix, as we cannot obtain relevant information from it as far as
tooling is concerned.

bootstrap now accepts --help usage flag

fix for #314 (rebar shell somehow blocks using io:format in gen_server handle_call)