add .yar extensions and fix a typo

https://www.bleepingcomputer.com/news/security/the-week-in-ransomware-august-31st-2018-devs-on-vacation/
is mentioned as the reference, and the picture has a space between “the” and “decryption”.

fix blackhole php regex

new yara rule for AsyncRAT

Snake Ransomware yara rule

Renamed poetRAT to avoid dupes + adjusted criteria

add .yar extension to the following email rules and add to indexes:

Email_fake_it_maintenance_bulletin
Email_generic_phishing.yar
Email_quota_limit_warning.yar

Signed-off-by: Ryan B <randomrhythm@rhythmengineering.com>

The regex for RAT_PoetRATPython was generating false positives. Adjusted
rule to need hits on at least 3 of the strings

Create extortion_email.yar

Poet Rat Rules

Add SHA3 (Keccak) round constants