Key-value store based on SingleNodeZab.

Currently the key-value store accepts PUT and GET HTTP requests.
To add an entry to the key-value store, do:

  curl localhost:8080/key -XPUT -d 'value'

To retrive the value for a given key, do:

  curl localhost:8080/key
Merge pull request #4 from m1ch1/master

Key-value store based on SingleNodeZab.