HashMap -> TreeMap for consistent collection index order in the keySet.
This should fix the
TestMissingMethodsError#testCollMissingPrintLnFlushX2 error with Bamboo,
expecting error on s[0], but that happened with s[1], since HashMap
keySet are not ordered.
Merge pull request #20 from Mind4SE/fix_jira_144

[fix_jira_144] Missing Methods detection test fix