Exclude composer.lock from dist file

Refs: #68 (comment)
Refs: #71

Author: WyriHaximus

.gitattributes

@@ -1,3 +1,6 @@
+# Set the default behavior, in case people don't have core.autocrlf set.
+* text eol=lf
+
 # Ignoring files for distribution archieves
 .github/ export-ignore
 etc/ export-ignore
@@ -8,6 +11,10 @@ var/ export-ignore
 .gitattributes export-ignore
 .gitignore export-ignore
 CONTRIBUTING.md export-ignore
+composer.lock export-ignore
 infection.json.dist export-ignore
 Makefile export-ignore
 README.md export-ignore
+
+# Diffing
+*.php diff=php