fix credentials location

Author: lohanidamodar

templates/dart/.travis.yml.twig

@@ -5,9 +5,9 @@ dart: stable
 os: linux
 
 install:
-- mkdir -p  ~/.pub-cache
+- mkdir -p  ~/.config/dart
 - |
-  cat <<EOF > ~/.pub-cache/credentials.json
+  cat <<EOF > ~/.config/dart/pub-credentials.json
     {
       "accessToken":"$PUB_ACCESS_TOKEN",
       "refreshToken":"$PUB_REFRESH_TOKEN",

templates/flutter/.travis.yml.twig

@@ -5,9 +5,9 @@ dart: stable
 os: linux
 
 install:
-- mkdir -p  ~/.pub-cache
+- mkdir -p  ~/.config/dart
 - |
-  cat <<EOF > ~/.pub-cache/credentials.json
+  cat <<EOF > ~/.config/dart/pub-credentials.json
     {
       "accessToken":"$PUB_ACCESS_TOKEN",
       "refreshToken":"$PUB_REFRESH_TOKEN",