topo.dotprops added

[dokato]

Needed for natverse/nat.nblast#44 to work.

See also:
natverse/nat.nblast#43

[coveralls]

Coverage increased (+0.06%) to 81.487% when pulling 45112ee on dokato:topodotp into 2da55fa on natverse:master.

[jefferis]

This looks good. I've just made a few small comments. Only other thing would be to add a test. Thanks! Greg.

[dokato]

Thanks @jefferis for your comments. All fixed, I added some test too and rebuilt the docs.

[jefferis]

Thank you!