Spanish Localization Added.

Conflicts:
	Reader.xcodeproj/project.pbxproj
Changed hardcoded constants to propertys with comments.
Changed all the compilers conditionals to use the new bools properties.

Conflicts:
	Sources/ReaderContentView.m
Added an import flag for ReaderConstants.h in ReaderViewController.
Added an example comment on ReaderDemoController of the way you can customize the Constants flags.
Fix on documentation of ReaderConstants.
Added ReaderColors to centralize some colors that con be customize. Added textColor and toolbarBackground color.
Fix on the documentation.