HtmlReporter: adding option to change output filename
HtmlReporter: adding option to change output filename

tjschuck/minitest-reporters,thinkthroughmath/minitest-reporters,thinkthroughmath/minitest-reporters,gavinlaking/minitest-reporters,kern/minitest-reporters,vadviktor/minitest-reporters,kern/minitest-reporters,vadviktor/minitest-reporters,gavinlaking/minitest-reporters,tjschuck/minitest-reporters