Allow for escaped ] characters in [] IDs

Allows for ] literal characters to be used within [] IDs by prefixing them with the \ character. `\` literal at the end of the  may be referenced by the `\\` sequence if conflicting. Under most circumstances the `\\` sequence will continue to work.

Potentially breaking change for users of [] ids that have `\\` anywhere in the id or `\` at the end of the id.

Fixes #1092

spec/tokenizer.js

@@ -146,6 +146,11 @@ describe('Tokenizer', function() {
     shouldMatchTokens(result, ['OPEN', 'ID', 'SEP', 'ID', 'CLOSE', 'OPEN', 'ID', 'SEP', 'ID', 'CLOSE']);
   });
 
+  it('allows escaped literals in []', function() {
+    var result = tokenize('{{foo.[bar\\]]}}');
+    shouldMatchTokens(result, ['OPEN', 'ID', 'SEP', 'ID', 'CLOSE']);
+  });
+
   it('tokenizes {{.}} as OPEN ID CLOSE', function() {
     var result = tokenize('{{.}}');
     shouldMatchTokens(result, ['OPEN', 'ID', 'CLOSE']);