rename calc_bonds

[hmacdope]

Rename calc_bonds to calc_distances, more correct name

@richardjgowers should we keep the Calc prefix? Now is the time to remove even if labour intensive

[pep8speaks]

Hello @hmacdope! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file distopia/tests/test_distopia.py:

Line 33:80: E501 line too long (83 > 79 characters)
Line 61:80: E501 line too long (82 > 79 characters)
Line 66:80: E501 line too long (86 > 79 characters)
Line 86:80: E501 line too long (89 > 79 characters)
Line 95:80: E501 line too long (93 > 79 characters)
Line 104:80: E501 line too long (97 > 79 characters)
Line 375:80: E501 line too long (87 > 79 characters)
Line 378:80: E501 line too long (96 > 79 characters)
Line 380:80: E501 line too long (100 > 79 characters)
Line 397:80: E501 line too long (108 > 79 characters)

[richardjgowers]

@hmacdope yeah I'm not wildly in love with calc_bonds as a name, but calc_distances is perhaps more vague, most the functions are calculating a distance of some sort. How about zip_distances? the logic being it's a bit like distance(a,b) for a, b in zip(c1, c2)

[richardjgowers]

also yeah calc_ everywhere is tiresome