Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/sebastian/diff/tests/fixtures/.editorconfig

@@ -0,0 +1 @@
+root = true

vendor/sebastian/diff/tests/fixtures/UnifiedDiffAssertTraitIntegrationTest/1_a.txt

@@ -0,0 +1 @@
+a

vendor/sebastian/diff/tests/fixtures/UnifiedDiffAssertTraitIntegrationTest/2_a.txt

@@ -0,0 +1,35 @@
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a

vendor/sebastian/diff/tests/fixtures/UnifiedDiffAssertTraitIntegrationTest/2_b.txt

@@ -0,0 +1,18 @@
+a
+a
+a
+a
+a
+a
+a
+a
+a
+a
+b
+a
+a
+a
+a
+a
+a
+c

vendor/sebastian/diff/tests/fixtures/out/.editorconfig

@@ -0,0 +1 @@
+root = true

vendor/sebastian/diff/tests/fixtures/out/.gitignore

@@ -0,0 +1,2 @@
+# reset all ignore rules to create sandbox for integration test
+!/**