get recursively all the contents under a directory

Added support for recursive=true when getting key value to get the whole
tree.
bug fix

You can't pass boolean to query string as it will treat it as "True" or
"False" with capital letter. etcd won't accept it, its case sensitive.
documentation updated with basic info

hope you don't mind. ;)
Merge pull request #3 from virtser/master

get recursively all the contents under a directory