Returns the blame at every revision of interest. Index is a datetime, column per committer, with number of lines
        blamed to each committer at each timestamp as data.

        :param branch: (optional, default 'master') the branch to work in
        :param limit: (optional, default None), the maximum number of revisions to return, None for no limit
        :param skip: (optional, default None), the number of revisions to skip. Ex: skip=2 returns every other revision, None for no skipping.
        :param num_datapoints: (optional, default=None) if limit and skip are none, and this isn't, then num_datapoints evenly spaced revs will be used
        :param committer: (optional, defualt=True) true if committer should be reported, false if author
        :param ignore_globs: (optional, default=None) a list of globs to ignore, default none excludes nothing
        :param include_globs: (optinal, default=None) a list of globs to include, default of None includes everything.
        :return: DataFrame

def cumulative_blame(self, branch='master', limit=None, skip=None, num_datapoints=None, committer=True,
                         ignore_globs=None, include_globs=None):
        """
        Returns the blame at every revision of interest. Index is a datetime, column per committer, with number of lines
        blamed to each committer at each timestamp as data.

        :param branch: (optional, default 'master') the branch to work in
        :param limit: (optional, default None), the maximum number of revisions to return, None for no limit
        :param skip: (optional, default None), the number of revisions to skip. Ex: skip=2 returns every other revision, None for no skipping.
        :param num_datapoints: (optional, default=None) if limit and skip are none, and this isn't, then num_datapoints evenly spaced revs will be used
        :param committer: (optional, defualt=True) true if committer should be reported, false if author
        :param ignore_globs: (optional, default=None) a list of globs to ignore, default none excludes nothing
        :param include_globs: (optinal, default=None) a list of globs to include, default of None includes everything.
        :return: DataFrame

        """

        revs = self.revs(branch=branch, limit=limit, skip=skip, num_datapoints=num_datapoints)

        # get the commit history to stub out committers (hacky and slow)
        if sys.version_info.major == 2:
            committers = set([x.committer.name for x in self.repo.iter_commits(branch, max_count=sys.maxsize)])
        else:
            committers = {x.committer.name for x in self.repo.iter_commits(branch, max_count=sys.maxsize)}

        for y in committers:
            revs[y] = 0

        if self.verbose:
            print('Beginning processing for cumulative blame:')

        # now populate that table with some actual values
        for idx, row in revs.iterrows():
            if self.verbose:
                print('%s. [%s] getting blame for rev: %s' % (
                str(idx), datetime.datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S'), row.rev,))

            blame = self.blame(rev=row.rev, committer=committer, ignore_globs=ignore_globs, include_globs=include_globs)
            for y in committers:
                try:
                    loc = blame.loc[y, 'loc']
                    revs.set_value(idx, y, loc)
                except KeyError:
                    pass

        del revs['rev']

        revs['date'] = to_datetime(revs['date'].map(datetime.datetime.fromtimestamp))
        revs.set_index(keys=['date'], drop=True, inplace=True)
        revs = revs.fillna(0.0)

        # drop 0 cols
        for col in revs.columns.values:
            if col != 'col':
                if revs[col].sum() == 0:
                    del revs[col]

        # drop 0 rows
        keep_idx = []
        committers = [x for x in revs.columns.values if x != 'date']
        for idx, row in revs.iterrows():
            if sum([row[x] for x in committers]) > 0:
                keep_idx.append(idx)

        revs = revs.ix[keep_idx]

        return revs