Fixing hidden pb when current progress is 0.

pb never prints the progress bar until the first task is completed.
Merge pull request #5 from rakyll/immediate-dump

Fixing hidden pb when current progress is 0
Move bar format into properties of ProgressBar

Also adds convenience method for setting format on a progress bar.
This change allows for customization of the format of individual
progress bars and also add a convenient, intuitive function for
setting the format:

pb.Format("[", "#", ">", ".", "]")
Format and setters
Update README
Fix README
Update pb_win.go

Don't use `github.com/AllenDang/w32` because 

- Too big for such a simple task 
- Issues using it on windows and after investigation and found (Unable to build w32)[https://github.com/AllenDang/w32/issues/34]
- Bug not relating to screen size can make your whole project fail to install

Wrote a small package to do this [github.com/olekukonko/ts](github.com/olekukonko/ts) and you are welcome as contributor 

Tested on windows & linux
Merge pull request #9 from olekukonko/patch-1

Update pb_win.go