Rename 'exp' snippet to more common snippet.

The old 'exp' with a block expectation becomes 'expb'.

snippets/ruby.snippets

@@ -995,6 +995,8 @@ snippet s.
 snippet spec
 	specify { subject.${0} }
 snippet exp
+	expect(${1:object}).to ${0}
+snippet expb
 	expect { ${1:object} }.to ${0}
 snippet raise
 	expect { ${1:object} }.to raise_error ${2:StandardError}, /${0:message_regex}/