better err message
Add comment about Systemd
Added lowercase RRClass and RRType tests per #108.

... need to add RRSIG covering type lowercased later.
Added lowercase RR tests where TTL is in play too.
Added lowercase test strings with RR class omitted
Committing @miekg patch from gist.

https://gist.github.com/miekg/f1b1fe6dba7d6b088eec
Added test to verify RRSIG type covered in mixed case.
Added couple failure tests for lowercase class/type
Changed test for lowercase tokens; improved code:

* for cases if $ORIGIN or $TTL are used in mixed case
* changed test name too
Fixed typo in "tokens"
Removed unnecessary toUpper.
Added tests to support mixed case Type and Class