Change constants to class variables

Because of the way that puppet's autoloader and pluginsync work,
modules on the master get loaded twice, which means that
you can't use Ruby constants at all w/o getting warning messages.

This commit changes all of the constants in `ini_file` to class
variables, which will avoid the warning messages.
Update Modulefile and CHANGELOG for 0.10.1 release
Merge pull request #44 from cprice-puppet/maint/master/change-constants-to-class-vars

Maint/master/change constants to class vars