Fixes escape character sequences that are not on the last attributes

src/absinthe_lexer.xrl

@@ -40,7 +40,7 @@ BlockStringValue        = """{BlockStringCharacter}*"""
 HexDigit            = [0-9A-Fa-f]
 EscapedUnicode      = u{HexDigit}{HexDigit}{HexDigit}{HexDigit}
 EscapedCharacter    = ["\\\/bfnrt]
-StringCharacter     = ([^\"{_LineTerminator}]|\\{EscapedUnicode}|\\{EscapedCharacter})
+StringCharacter     = ([^\\"{_LineTerminator}]|\\{EscapedUnicode}|\\{EscapedCharacter})
 StringValue         = "{StringCharacter}*"
 
 % Boolean Value

test/absinthe/phase/parse/block_strings_test.exs

@@ -27,6 +27,37 @@ defmodule Absinthe.Phase.Parse.BlockStringsTest do
     assert "slashes \\\\ \\/" == extract_body(result)
   end
 
+  test "parses attributes when there are escapes" do
+    assert {:ok, result}  = run(
+      ~s<{ post(title: "title", body: "body\\\\") { name } }>
+    )
+    assert "body\\" == extract_body(result)
+
+    assert {:ok, result}  = run(
+      ~s<{ post(title: "title\\\\", body: "body") { name } }>
+    )
+    assert "body" == extract_body(result)
+  end
+
+  test "parse attributes where there are escapes on multiple lines" do
+    assert {:ok, result}  = run(
+      ~s<{ post(
+        title: "title",
+        body: "body\\\\"
+      ) { name } }>
+    )
+    assert "body\\" == extract_body(result)
+
+    assert {:ok, result}  = run(
+      ~s<{ post(
+        title: "title\\\\",
+        body: "body"
+      ) { name } }>
+    )
+    assert "body" == extract_body(result)
+  end
+
+
   @input [
     "",
     "    Hello,",