add support for new recommended "context" scope

Author: stevenchanin

Snippets/after_context.sublime-snippet

@@ -0,0 +1,8 @@
+<snippet>
+  <content><![CDATA[after(:context) do
+  $0
+end]]></content>
+  <tabTrigger>aftc</tabTrigger>
+  <scope>source.ruby.rspec</scope>
+  <description>after(:context) do … end</description>
+</snippet>

Snippets/before_context.sublime-snippet

@@ -0,0 +1,8 @@
+<snippet>
+  <content><![CDATA[before(:context) do
+  $0
+end]]></content>
+  <tabTrigger>befc</tabTrigger>
+  <scope>source.ruby.rspec</scope>
+  <description>before(:context) do … end</description>
+</snippet>