Update simplecov version to 0.14.1

[potomak]

Note: simplecov 0.14.0 fixed an issue that was breaking the example at
spec/coveralls/simplecov_spec.rb:75.

Before the result of #get_source_files for fixtures/sample.rb was:

00 COUNTED - # Foo class
01 COUNTED - class Foo
02 COUNTED -   def initialize
03 COUNTED -     @foo = 'baz'
04 COUNTED -   end
05 COUNTED -
06 COUNTED -   # :nocov:
07 SKIPPED -   def bar
08 SKIPPED -     @foo
09 SKIPPED -   end
10 COUNTED -   # :nocov:
11 COUNTED - end

Using simplecov 0.14.1, that includes
simplecov-ruby/simplecov#551, the result is:

00 COUNTED - # Foo class
01 COUNTED - class Foo
02 COUNTED -   def initialize
03 COUNTED -     @foo = 'baz'
04 COUNTED -   end
05 COUNTED -
06 SKIPPED -   # :nocov:
07 SKIPPED -   def bar
08 SKIPPED -     @foo
09 SKIPPED -   end
10 SKIPPED -   # :nocov:
11 COUNTED - end

[potomak]

It seems like there's already an open PR to address this.