EOSIO API Healthcheck for HAProxy

This program implements EOSIO healthcheck for HAProxy over TCP.

TCP Protocol

The protocol is simple and has 4 rules.

Data is transmitted in packets encoded in ascii and ends with newline \n.
There are two types of packages: Request and Response. Each Request has exactly one Response.
Each parameter inside a Request is separated by |
Each response contains exactly one status code (see below)

The following parameters are supported in a request and are ordered from first to last below:

#	Name	Required	Description
1	Host	Yes	IP/Hostname to the api.
2	Port	No	Port number to the api (default `80`)
3	num_blocks	No	Number of blocks the api can drift before reported `down` (default 10)
4	version	No	API Version to check against, `v1` = standard, `v2` = Hyperion (default `v1`)

The api can respond with exactly one status code. See HAproxy documentation for more information

code	Description
`up`	Api is healthy
`down`	Api is not healthy
`failed`	The program failed to read the status from the api.
`maint`	Api is set in maintenance mode (not used)
`ready`	Api is ready again after being in `maint` state (not used)
`stopped`	Api has been stopped manually (not used)