Use NS_ENUM and NS_OPTIONS for the log level and log flags

You can just pick fd9d3ed if you only want the enums/options.
This change does make CocoaLumberjack more Swift-friendly, but more work will be needed to make it viable.
The problem with using any Swift code is that it bumps the minimum OS requirement to iOS 7/OS X 10.9. That and using Swift code with static libraries is tricky, as there isn’t a way to actually build a static library that has Swift code in it.
> On Oct 5, 2014, at 8:15 PM, Ernesto Rivera <notifications@github.com> wrote:
> 
> In Classes/CocoaLumberjack.h:
> 
> > @@ -65,3 +67,6 @@
> >  #import "DDTTYLogger.h"
> >  #import "DDASLLogger.h"
> >  #import "DDFileLogger.h"
> > +
> > +// Legacy
> > +#import "DDLegacy.h"
> That's a good thing! Unluckily I still have to maintain iOS 6 projects, so not using Swift just yet.
> 
> Do you think the proposed changes will play nicely with Swift (#299 <https://github.com/CocoaLumberjack/CocoaLumberjack/issues/299>)?
> Probably we will need a CocoaLumberjack.swift (#225 <https://github.com/CocoaLumberjack/CocoaLumberjack/issues/225>).
> 
> —
> Reply to this email directly or view it on GitHub <https://github.com/CocoaLumberjack/CocoaLumberjack/pull/338/files#r18439875>.
>