Remove warning about unused local variable.

This removes the warning that was occurring by passing the `HTMLFormatter#binding` to a erb template without using that variable in the method.

The binding given to the erb template is that of a basic object that has no methods or variables apart from accessor methods. This hides the internals of`HTMLFormatter` from the ERB template.

This change was tested locally against the cucumber-ruby-core project.

Please consider a 0.8.1 release as this warning has propagated down to other projects that depend on simplecov-html.
This is the downside of simplecov being a rather low-level tool - I've had plenty of reports about ruby warnings all around and yes, while it is incredibly silly to have this workaround in place, people seem to want warning-free libraries. Also, this particular piece broke the gem when I got a PR that removed the assignment and then in the vie the variable didn't exist :/

On 3. August 2014 14:39:49 MESZ, Benjamin Fleischer <notifications@github.com> wrote:
>> @@ -55,8 +55,21 @@ def formatted_source_file(source_file)
>>    # Returns a table containing the given source files
>>    def formatted_file_list(title, source_files)
>>      title_id = title.gsub(/^[^a-zA-Z]+/,
>'').gsub(/[^a-zA-Z0-9\-\_]/, '')
>> -    title_id # Ruby will give a warning when we do not use this
>except via the binding :( FIXME
>> -    template('file_list').result(binding)
>> +    data = FileListData.new(title, title_id, source_files)
>
>This seems like overkill, no?
>
>---
>Reply to this email directly or view it on GitHub:
>https://github.com/colszowka/simplecov-html/pull/24/files#r15734293