spamassassin: fixed Haraka crash when spamd_response.headers not defined

happens when local SA config doesn't enable that header and results in this:

[CRIT] [-] [core] ReferenceError: Invalid left-hand side in assignment
    at Socket.<anonymous> (/usr/local/haraka/plugins/spamassassin.js:88:13)
Merge pull request #583 from msimerson/spamassassin

spamassassin: fixes Haraka crash when spamd_response.headers not defined
update test to use 4.2.2.2 as 'test' hostname/ip
Merge pull request #589 from msimerson/testfix

update test to use 4.2.2.2 as 'test' hostname/ip
helo.checks: make match_re work

1. precompile the regex list at load time (was: compile every regex on every connection)

2. test regexes, ignore and log error for bad ones

3. load .ini and regex list at register() with config parsing callback (was at connect())

4. added tests for match_re