coverage discrepancy bug fix + some additional features

[katzoded]

thanks for providing this tool :-)
we are using it in CI and we have made few additional features.
lately we found out that there is some discrepancies in coverage related to parse_gcov_file this issue was addressed (please see an example for one of those problematic .gcov).

• since line 19 repeats multiple times within the same file, for each of those repetition the output would create another entry (another line) which shifts all the coverage report beyond this point!
• code for this fix is in here

        -:   15:
        -:   16:class future_base_t
        -:   17:{
        -:   18:public:
    #####:   19:    virtual ~future_base_t() = default;
------------------
_ZN5async13future_base_tD0Ev:
    #####:   19:    virtual ~future_base_t() = default;
------------------
_ZN5async13future_base_tD2Ev:
    #####:   19:    virtual ~future_base_t() = default;
------------------
        -:   20:    virtual void cancel() = 0;
        -:   21:};
        -: 

on top of that, I'm sharing other feature we have added to coveralls

• --parallel in report
• finish_report for competing a parallel report