Drop support of Mac OS 10.9

- set minimum deployment target to 10.10
- set minimum system version to 10.10

atom/browser/resources/mac/Info.plist

@@ -23,7 +23,7 @@
   <key>LSApplicationCategoryType</key>
   <string>public.app-category.developer-tools</string>
   <key>LSMinimumSystemVersion</key>
-  <string>10.9.0</string>
+  <string>10.10.0</string>
   <key>NSMainNibFile</key>
   <string>MainMenu</string>
   <key>NSPrincipalClass</key>

brightray/brightray.gypi

@@ -32,7 +32,7 @@
       'GCC_ENABLE_CPP_RTTI': 'NO',
       'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES',
       'CLANG_CXX_LANGUAGE_STANDARD': 'c++14',
-      'MACOSX_DEPLOYMENT_TARGET': '10.9',
+      'MACOSX_DEPLOYMENT_TARGET': '10.10',
       'RUN_CLANG_STATIC_ANALYZER': 'YES',
       'USE_HEADER_MAP': 'NO',
     },