Use CGI instead of URI in params processing

(Looks like this got flipped back during a merge before)
move some methods from Keen::Client to Keen:Helpers
move config variable to a config class
dup the default option hash
simplify way to call api_headers
add a query class
add ability to save a query in Keen
add methods delete and saved to get a query
keep possiblity to run queries specific to a keen client instance
keep compability with previous way to configure the gem
move ensure project id
separate query and saved query
update Readme