stream command fixes, bitpos fix, exec fix

• fix BITPOS error (thanks @xiaoyuzdy)
• small fixes for XREAD, XACK, and XDEL. Mostly error cases.
• fix empty EXEC return type (thanks @ashanbrown)
• fix XDEL (thanks @svakili and @yvesf)
• fix FLUSHALL for streams (thanks @svakili)

lua fix and redis 6.0.10

• fix problem where Lua code didn't set the selected DB
• update to redis 6.0.10 (thanks @lazappa)

LUA update, channel fix

• update LUA dependency
• deal with (p)unsubscribe when there are no channels

mod tidy

• clean up dependencies removed in v2.14.0. Thanks @johejo!

RESP3

• support for HELLO and the RESP3 protocol
• KEEPTTL in SET (thanks @johnpena)

XREAD and go1.15

• support Go 1.14 and 1.15
• update the Check...() methods
• support for XREAD (thanks @pieterlexis)

test setup change

• Use SAN instead of CN in self signed cert for testing (thanks @johejo)
• Travis CI now tests against the most recent two versions of Go (thanks @johejo)
• changed unit and integration tests to compare raw payloads, not parsed payloads
• remove "redigo" dependency

HSTRLEN and AUTH

• added HSTRLEN
• minimal support for ACL users in AUTH

TLS and SetError

• added RunTLS(...)
• added SetError(...)

redis 6 and smaller fixes

• test against redis 6
• Lua json update (thanks @gsmith85)
• CLUSTER commands (thanks @kratisto)
• fix TOUCH
• fix a shutdown race conditionv