Update pad times to use for hits considered for clustering

[bryngemark]

This motivates the new pad times, -2.9 for Pad1 (red), -2.7 for 2 (blue) and 0 (unchanged) for 3 (orange).

[bryngemark]

This resolves #49

[bryngemark]

any comments @rodwyer100 @awhitbeck @GNiramay ?

[awhitbeck]

sounds reasonable to me

[rodwyer100]

This seems like a needed change, and also one that could change how useful timing would be for electron counting. It makes me tempted to look into an older project :). Cool.