first rev with binary protocol support

[stephas]

this should give mctop binary protocol support.

• will dynamically decide if the packet is binary or ascii protocol
• first rev filters opcode 1, e.g. set to extract keys
• also replaces unprintable characters with '~'

thank you etsy.

[scurvy]

While this does add binary support, it breaks compatibility with Ruby 1.8.7.

[Sean-Der]

@stephas Awesome, thanks for the PR.

mctop hasn't seen an activity in about a year, but that is about to change.
I am going to go through and review all the smaller feature PRs, merge those and tag a release.

After that is done I am going to start adding binary support to mctop. After all the merging and other work I don't know how well this patch will land. Either way I would love your help in the near future.

[gdubicki]

I confirm that it works on Ruby 1.9.2 and Memcached 1.4.17 on Centos 5. But I had to also apply this #24 to make it work.