Merge pull request #6 from fitzgen/master

Update protocol to describe loading sources
Document Debugger.Object.prototype.unsafeDereference.
Clarify actors' different communication patterns.
Document safe getter value descriptors.
Add 'enumerable' and 'writable' props to safe getter value descriptors.
Fix typo in safeGetterValues example.
Tweak description of 'sources' request and source actors.
Document Debugger.Script.prototype.sourceMapURL.
Spell out effect of duplicate debuggee adds.
Add docs for "prototypesAndProperties".
Merge pull request #12 from MHordecki/b795979

Add docs for a new packet type "prototypesAndProperties".
Merge remote-tracking branch 'jimb/master' into blackbox

Conflicts:
	protocol