rebar_config:is_verbose/0: fix variable name
rebar_log: use defines for log level numbers
Change default log level to 'warn' and introduce -q/--quiet
Write ERROR messages to standard_error device
Fix is_verbose/1 helper function
Merge pull request #184 from tuncer/logging

Fix log levels
rebar_dia_compiler: fix Dialyzer warnings
bootstrap: avoid trying to run 'debug' command

If you invoke 'make debug', then bootstrap executes rebar:main/1 with
the extra argument "debug" and rebar treats that as a command. There is
no such command.

Without this patch you will see the following on bootstrap:
Command 'debug' not understood or not applicable
Merge pull request #199 from tuncer/dia-dialyzer-warnings

rebar_dia_compiler: fix Dialyzer warnings
Merge pull request #200 from tuncer/fix-debug-bootstrap

bootstrap: avoid trying to run 'debug' command