Ignore test name suffix generated by GOMAXPROCS

Hi, In issue #14 and 1daba18ac3 you changed the parser to accept test name that suffixed with `-N` and now the parser generates the report with suffix `-N`.
However these suffix is usually generated by `go test` with explicit GOMAXPROCS env val.

For example, `GOMAXPROCS=3 go test -v|go2xunit` will generate the below.
```
...
<testcase classname="github.com/tebeka/go2xunit" name="Test_nameWithNum-3" time="0.00">
...
```

Thus, in most situations, `-N` is NOT a part of ideal test name and noisy.
So in this request, I want to change to handle these suffix as an ignored part of  regex, not the name.