Update lib/minitest/reporters/default_reporter.rb

I had a problem with the following error when trying to run a test file individually from within RubyMine:

/Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/activesupport-3.2.9/lib/active_support/core_ext/time/calculations.rb:326:in `-': can't convert nil into an exact number (TypeError)




	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/activesupport-3.2.9/lib/active_support/core_ext/time/calculations.rb:326:in `minus_with_duration'




	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/activesupport-3.2.9/lib/active_support/core_ext/time/calculations.rb:337:in `minus_with_coercion'
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporters/default_reporter.rb:139:in `after_test'
F	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporters/default_reporter.rb:41:in `pass'
a	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:77:in `public_send'
b	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:77:in `block in trigger_callback'
u	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:76:in `each'
l	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:76:in `trigger_callback'
o	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:61:in `record'
u	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:887:in `block in _run_suite'
s	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:876:in `map'
 	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:876:in `_run_suite'
t	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:30:in `_run_suite'
e	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:863:in `block in _run_suites'
s	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:863:in `map'
t	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:863:in `_run_suites'
s	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-reporters-0.13.1/lib/minitest/reporter_runner.rb:22:in `_run_suites'
 in 0.165924s, 36.1611 tests/s, 6.0269 assertions/s.
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:836:in `_run_anything'




	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:1025:in `run_tests'
6 tests, 1 assertions, 0 failures, 0 errors, 0 skips	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:1012:in `block in _run'
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:1011:in `each'
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:1011:in `_run'
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:1000:in `run'
	from /Users/mcowden/.rvm/gems/ruby-1.9.2-p290@ruby1.9/gems/minitest-4.1.0/lib/minitest/unit.rb:758:in `block in autorun'
Coverage report generated for Unit Tests to /Users/mcowden/Development/bna/bas/test/models/coverage. 0 / 0 LOC (0.0%) covered.
Add handling for when runner.test_start_time is nil

When running in an older version of minitest, our selenium
integration (based on MiniTest::Spec) does not call #before_test
before calling #print_test_with_time for the first time.
Defaulting test_start_time to Time.now does not seem to effect
the rest of the test run, and times are reported correctly.
Merge branch 'master' of https://github.com/wanelo/minitest-reporters into develop
Fix the test_start_time bug in all other reporters.
Bump version.