refactor sumo.conf recipe and erb

There is a lot of code duplication going on in the sumoconf.rb recipe.
This removes much of that and combines the associated erb files.
clean up if statement
remove unused attrib

Removing ['sumologic']['sources']['default_timezone'] as it's blocking
the new definition where ['sumologic']['sources'] is an array instead
of a hash and maps directly to the sources used in the sumo.json.

As far as I can tell, this attribute was never, ever
used for anything in this cookbook.

And it's marked as required!!!
Add support for setting the sources list via attributes

This allows you to specify the complete source list for a given host
in env/role/node/cookbook attributes.

Note that until the client side of the REST API for updating a hosts
sources list is implemented in this cookbook, this will only allow
setting of the sources list at install time.
remove dup lines

Already removed default_timezone two commits ago, but it looks like
there was an accidental copy/paste duplication of installDir here.
Merge pull request #20 from lithiumtech/master

Support setting full sources list via attributes and refactor sumoconf recipe.