Merge pull request #1 from oriordan/multiple-target-support

Adding support for multiple targets in URL
a single bad metric shouldn't kill the entire request
Merge pull request #2 from oriordan/implicit-until-now

Implicit until now
Better handling of from and until parameters:
 - parsing Graphite date formats (HH:MM_YYYYMMDD, YYYYMMDD, MM/DD/YY)
 - if not specified, until defaults to now
 - if not specified, from defaults to now - 24 hours