Sometimes, the text after "# " shows the name of the test binary
("<package>.test") in addition to the package
e.g.: "# package/name [package/name.test]".
This change ensures that the packages' build outputs are associated
correctly in this case.
Mainly:
* Moving the averaging/merging of benchmarks from the parser to the formatter package
* Tightening up the regex so it only captures the numeric values (no more of trimming spaces and the ns/op)
* Deleting the writing up in xml file the benchmark memory sections of B/op and Allocs/op
Also added a test case for parseNanoseconds().
