apply custom consumer tag to consumer if supplied

[andreaseger]

This fixes #92 and creates the consumer with a custom consumer_tag if one is supplied, otherwise the previous behaviour of using the auto-generated one is maintained.

Some Notes:

• I placed the consumer_tag as third parameter in Channel#basic_consume to keep the interface the same as the delegated java method.
• in the recover_from_network_failure case I recreate a consumer with the same consumer tag - so it would use a custom supplied one. I'm not sure in which cases this method is exaclty called and if there are any edge cases to consider when reusing the same consumer_tag.
• I wasn't entirely sure where to put the specs for this, but the basic_consume_specs seemed like a good place.

[michaelklishin]

This is a breaking API change but OK, we'll bump the version as it's better than any of the alternatives I can think of.

[andreaseger]

I don't think is it really a breaking change?

if you call it with 3 parameter the last one will be consumer - this is the same behaviour as before.
if you call it with 4 you have both consumer_tag and consumer

[michaelklishin]

Wow, in a decade with Ruby I haven't seen a method where arguments with default values weren't at the end of the argument list. That indeed works as you describe:

2.2.2 :001 > def abc(a, b, c = nil, d)
2.2.2 :002?>   [a, b, c, d]
2.2.2 :003?>   end
 => :abc
2.2.2 :004 > abc(1, 2, 3, 4)
 => [1, 2, 3, 4]
2.2.2 :005 > abc(1, 2, 4)
 => [1, 2, nil, 4]

Perfect, I'm going to QA it right away then. Thank you.

[andreaseger]

sorry for the typo in the specs - somehow missed that