(TK-5) Remove --config requirement

TrapperKeeper no longer requires a --config argument from the
command line. If this argument is just provided,
parse-config-data will simply return a map containing nothing but
the :debug field.
(TK-5) Add new tests

Add new tests to test omitting the --config arg. The tests
will make sure that the cli args and the config data can
be successfully parsed.
(TK-5) Update parse-config-data docstring

Update the docstring on parse-config-data. It now lists all the
proper file extensions that TK accepts for configuration data,
and explains what happens when no configuration data is specified.
Reformat docstring for parse-config-data

Reformat the docstring for parse-config-data so that there are
no more than 80 characters per line.
(TK-5) Add dummy assertions

Add dummy assertions to the end of added test cases, as these
test cases simply run a function and fail if an exception
was generated.
Merge pull request #155 from fpringvaldsen/make-config-optional

(TK-5) Make --config optional