Implement italics in package

Closes #3

tex/latex/sourceserifpro/sourceserifpro.sty

@@ -8,7 +8,7 @@
 % Licenced under the LPPL v1.3 or higher.
 %
 \NeedsTeXFormat{LaTeX2e}[1994/12/01]
-\ProvidesPackage{sourceserifpro}[2016/04/08 v1.2 Adobe's Source Serif Pro typeface]
+\ProvidesPackage{sourceserifpro}[2018/09/05 v1.3 Adobe's Source Serif Pro typeface]
 
 \RequirePackage{ifxetex,ifluatex,xkeyval}
 
@@ -121,26 +121,34 @@
 	% Regular/Bold
 	\newfontfamily\sourceserifpro
 		[ UprightFont    = *-Regular ,
-		  BoldFont       = *-Bold ]
+		  ItalicFont     = *-RegularIt ,
+		  BoldFont       = *-Bold ,
+		  BoldItalicFont = *-BoldIt ]
 		{SourceSerifPro}
 
 	% Light/Semibold
 	\newfontfamily\sourceserifprolight
 		[ UprightFont    = *-Light ,
-		  BoldFont       = *-Semibold ]
+		  ItalicFont     = *-LightIt ,
+		  BoldFont       = *-Semibold ,
+		  BoldItalicFont = *-SemiboldIt ]
 		{SourceSerifPro}
 
 	% ExtraLight/Black
 	\newfontfamily\sourceserifproextreme
-		[ UprightFont    = *-ExtraLight  ,
-		  BoldFont       = *-Black  ]
+		[ UprightFont    = *-ExtraLight ,
+		  ItalicFont     = *-ExtraLightIt ,
+		  BoldFont       = *-Black ,
+		  BoldItalicFont = *-BlackIt ]
 		{SourceSerifPro}
 
 	% Lining figures
 	\newfontfamily\sourceserifprolf
 		[ Numbers        = \sourceserifpro@figurealign ,
 		  UprightFont    = *-\sourceserifpro@regstyle ,
-		  BoldFont       = *-\sourceserifpro@boldstyle ]
+		  ItalicFont     = *-\sourceserifpro@regstyle It ,
+		  BoldFont       = *-\sourceserifpro@boldstyle ,
+		  BoldItalicFont = *-\sourceserifpro@boldstyle It ]
 		{SourceSerifPro}
 
 	% Dont keep all default font features