Use keys method from Hash

Signed-off-by: Laurent Arnoud <laurent@spkdev.net>
weeks added to output (using :weeks => true)
read me updated
now prefixing with '1' if string starts with recognized word but no number, ie. 'day'
weeks fixed
Adds :units option. Also:

* Removes Jeweler, not needed (http://railscasts.com/episodes/245-new-gem-with-bundler)
* Remove duplicated piece of code
* Upgrades RSpec and Bundler
Merge pull request #15 from mauriciozaffari/master

Adds :units option. Also:
Fixes #16 - Output should parse correctly

Improved spec examples to include durations with
years and added a spec to cover round tripping 
durations that need to be output and then 
re-parsed, for example when populating form fields 
in a web app.
Merge pull request #17 from errm/master

Fixes #16 - Output should parse correctly
Fix inserting zero in front of number after decimal point with format :chrono
Fix output if seconds end with .0
Fill with zeros in chrono output if seconds are 0
First pass at file changes
Ignore the right files
Don't commit Gemfile.lock
Merge pull request #11 from spk/map_keys

Use keys method from Hash
Merge pull request #14 from phulst/master

now prefixing with '1' if string starts with recognized word but no number, ie. 'day'
Spec refactor
Resolve conflicts
Better specs