Fix nested code blocks inside lists

This is now parsed correctly:
---
 -      test
---

lib/lexer_block/list.js

@@ -78,6 +78,7 @@ function skipOrderedListMarker(state, startLine) {
 module.exports = function list(state, startLine, endLine, silent) {
   var nextLine,
       indent,
+      oldTShift,
       oldIndent,
       oldTight,
       start,
@@ -163,7 +164,9 @@ module.exports = function list(state, startLine, endLine, silent) {
 
     oldIndent = state.blkIndent;
     oldTight = state.tight;
-    state.blkIndent = state.tShift[startLine] = indent;
+    oldTShift = state.tShift[startLine];
+    state.tShift[startLine] = contentStart - state.bMarks[startLine];
+    state.blkIndent = indent;
     state.tight = true;
 
     state.lexerBlock.tokenize(state, startLine, endLine, true);
@@ -176,7 +179,8 @@ module.exports = function list(state, startLine, endLine, silent) {
     // but we should filter last element, because it means list finish
     prevEmptyEnd = (state.line - startLine) > 1 && isEmpty(state, state.line - 1);
 
-    state.blkIndent = state.tShift[startLine] = oldIndent;
+    state.blkIndent = oldIndent;
+    state.tShift[startLine] = oldTShift;
     state.tight = oldTight;
 
     state.tokens.push({ type: 'list_item_close' });