Net::SSH.start returns result of block

It's useful (and expected) to have the result of evaluating a block
returned.  Net::HTTP.start has this behavior, for example.  Updated
Net::SSH to have the same behavior.
PacketStream: Properly detect disconnects in nonblocking reads.

We see a bug where it's possible to get net-ssh into an infite loop
spinning CPU after a connection has been closed. I am unable to
reliably reproduce it, so I can't be positive this is the fix, but I
have not seen a recurrence in our environment since adding this patch.
Add stderr handling to Net::SSH::Test

Add #gets_extended_data to the test flow
Fix Invalid key size in JRuby
Merge pull request #64 from mhuffnagle/master

Net::SSH.start now returns result of block
Merge pull request #67 from ohrite/test_extended_data

Add stderr handling to Net::SSH::Test
Updated readme re: ruby 1.8
Update test readme
Merge pull request #68 from ohrite/jruby_key_size

Fix Invalid key size in JRuby
Merge remote-tracking branch 'origin/master' into 2.6
Updated test readme for jruby 1.6
Added jruby 1.6 fix to readme
Last fully supported ruby 1.8 release is 2.5.1
Version bump (2.6.2)
Merge pull request #65 from nelhage/async-disconnect

PacketStream: Properly detect disconnects in nonblocking reads.
Updated changelog
Removing warnings
Merge pull request #71 from HerbCSO/fix-warnings

Removing warnings
Merged
Remove a warning to load mocha

For this message.

    *** Mocha deprecation warning: Change `require 'mocha'` to `require 'mocha/setup'`.