Hammer CLI

When one of yaml config files has wrong syntax (for example tab instead of space indentation) hammer fails without telling the user what actually happened and which file the issue is in:

/home/vagrant/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/psych.rb:370:in `parse': (<unknown>): did not find expected key while parsing a block mapping at line 2 column 1 (Psych::SyntaxError)
    from /home/vagrant/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/psych.rb:370:in `parse_stream'
    from /home/vagrant/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/psych.rb:318:in `parse'
    from /home/vagrant/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/psych.rb:245:in `load'
    from /home/vagrant/hammer/hammer-cli/lib/hammer_cli/settings.rb:37:in `load_from_file'
    from /home/vagrant/hammer/hammer-cli/lib/hammer_cli/settings.rb:20:in `block in load_from_paths'
    from /home/vagrant/hammer/hammer-cli/lib/hammer_cli/settings.rb:16:in `each'
    from /home/vagrant/hammer/hammer-cli/lib/hammer_cli/settings.rb:16:in `load_from_paths'
    from ./bin/hammer:49:in `<main>'

Hammer should print more informative message, for example:

Couldn't load configuration file '/home/vagrant/.hammer/cli_config.yml', please check the file syntax.