Add --dump-response flag

[ppfeister]

Closes #2205

Sample interaction:

$ sherlock --site github ppfeister --dump-response
[*] Checking username ppfeister on:

+++++++++++++++++++++
TARGET NAME   : GitHub
USERNAME      : ppfeister
TARGET URL    : https://www.github.com/ppfeister
TEST METHOD   : status_code
Results...
RESPONSE CODE : 200
>>>>> BEGIN RESPONSE TEXT

<<<<< END RESPONSE TEXT
VERDICT       : Claimed
+++++++++++++++++++++
[+] GitHub: https://www.github.com/ppfeister

[*] Search completed with 1 results

Users experiencing F+ or F- can use the flag to more easily share site output and results, and contributors can use the flag to more easily debug targets.