don't force KissMetrics to record page views

There's already an option on the KissMetrics website that will turn this on as part of loading the KissMetrics package. If you want to track every page view, you should just turn that on instead.
only read the config file once, clean up a bit
allow the config file location to be passed as :config
raise an explanatory error when the config is bad

fixes #30
handle empty environment configs
reverse merge so that config stays a HWIA (oops)
remove useless use of inject
remove duplication of parent class code
raise a nicer error when KissMetrics has no js_url_key
allow Analytical.config without explicit nil arg
Only add setDomainName if the :domain key is set, just like allowLinker. Seems weird to _setDomainName '' if you're tracking a single site
Adding Gauges support!
Merge pull request #44 from sfsekaran/gauges

Adding Gauges support!
Merge pull request #36 from indirect/unforced_kissmetrics

don't force KissMetrics to record page views
Merge pull request #37 from indirect/module_names

Handle missing module names
Merge pull request #41 from johnpaulashenfelter/patch-1

Only add setDomainName if the :domain key is set, just like allowLinker....
Hard-code the HTML format for the analytical_javascript partial.
Keep explicit format but remove .erb handler because passing handlers as extensions is deprecated in rails 3.2.
Pass in format and handler as hash keys for rails 4 compatibility.
fix tests