Fix spec errors with binding of caller

For some weird reason with binding of caller loaded the inspected value
for strings is no longer quoted, breaking the specs, so this changes
the specs back to using all symbols.

spec/better_errors/error_page_spec.rb

@@ -10,10 +10,10 @@ module BetterErrors
 
     let(:exception_binding) {
       local_a = :value_for_local_a
-      local_b = "value_for_local_b"
+      local_b = :value_for_local_b
 
       @inst_c = :value_for_inst_c
-      @inst_d = "value_for_inst_d"
+      @inst_d = :value_for_inst_d
 
       binding
     }
@@ -39,15 +39,15 @@ module BetterErrors
           expect(html).to include('<td class="name">local_a</td>')
           expect(html).to include("<pre>:value_for_local_a</pre>")
           expect(html).to include('<td class="name">local_b</td>')
-          expect(html).to include('<pre>"value_for_local_b"</pre>')
+          expect(html).to include("<pre>:value_for_local_b</pre>")
         end
 
         it "shows instance variables" do
           html = error_page.do_variables("index" => 0)[:html]
           expect(html).to include('<td class="name">' + '@inst_c</td>')
           expect(html).to include("<pre>" + ":value_for_inst_c</pre>")
           expect(html).to include('<td class="name">' + '@inst_d</td>')
-          expect(html).to include("<pre>" + '"value_for_inst_d"</pre>')
+          expect(html).to include("<pre>" + ":value_for_inst_d</pre>")
         end
 
         it "does not show filtered variables" do
@@ -56,7 +56,7 @@ module BetterErrors
           expect(html).to include('<td class="name">' + '@inst_c</td>')
           expect(html).to include("<pre>" + ":value_for_inst_c</pre>")
           expect(html).not_to include('<td class="name">' + '@inst_d</td>')
-          expect(html).not_to include("<pre>" + '"value_for_inst_d"</pre>')
+          expect(html).not_to include("<pre>" + ":value_for_inst_d</pre>")
         end
 
         it "does not inspect value of ignored classes" do
@@ -65,11 +65,11 @@ module BetterErrors
           expect(html).to include('<td class="name">local_a</td>')
           expect(html).not_to include("<pre>:value_for_local_a</pre>")
           expect(html).to include('<td class="name">local_b</td>')
-          expect(html).to include('<pre>"value_for_local_b"</pre>')
+          expect(html).not_to include("<pre>:value_for_local_b</pre>")
           expect(html).to include('<td class="name">' + '@inst_c</td>')
           expect(html).not_to include("<pre>" + ":value_for_inst_c</pre>")
           expect(html).to include('<td class="name">' + '@inst_d</td>')
-          expect(html).to include("<pre>" + '"value_for_inst_d"</pre>')
+          expect(html).not_to include("<pre>" + ":value_for_inst_d</pre>")
           expect(html).to include("(Class ignored. Remove Symbol from BetterErrors.ignored_classes if you need to see it.)")
         end