Register chance as an anonymous AMD module

Instead of as the named module 'Chance' - basic fix for #49
Merge pull request #50 from daedalus28/patch-1

Register chance as an anonymous AMD module
Use natural in place of integer
Fix default options
Merge pull request #54 from ichernev/fix-integer

Use natural in place of integer
Merge branch 'develop'
Bump package version number
Automatically rewritten for npm.