Add context functionality

[asenchi]

This allows one to set a context earlier in an application or provide a
context for a block.

[mmcgrana]

Is there an example available of how this would be used in an app and what the results would be? This would help illustrate the problem that this is trying to solve.

[asenchi]

Sure, so I see two uses that people have requested and this PR fulfills. One was yours and another Fabio's.

Scrolls.context(:request_id => "f49f0ba0-7073-012f-6f14-64ce8f596974") do
  request_method
end

This would prefix every Scrolls.log call within the block.

Scrolls.context(:app => :railgun, :deploy => "production")

This would prefix all Scrolls.log usage for the entire application.

[mmcgrana]

Right. Here is an executation example that further illustrates how this works:

1.9.2p318 :001 > require "./lib/scrolls"
 => true 
1.9.2p318 :002 > Scrolls::Log.start
 => true 
1.9.2p318 :003 > Scrolls.context(:global => "g")
 => nil 
1.9.2p318 :004 > Scrolls.log(:local => "l")
global=g local=l
 => nil 
1.9.2p318 :005 > Scrolls.context(:around => "a") { Scrolls.log(:local => "l") }
global=g around=a local=l
 => {:global=>"g"} 
1.9.2p318 :006 > Scrolls.context(:around => "a") { Scrolls.context(:inner => "i") { Scrolls.log(:local => "l") } }
global=g around=a inner=i local=l
 => {:global=>"g", :around=>"a"} 
1.9.2p318 :007 > Scrolls.log(:local => "l")
global=g around=a local=l

Actually that last bit might be a bug?

[asenchi]

Yep, that last one is a bug. I think I see what is happening.