pgsanity should work sanely when encountering a unicode BOM

[markdrago]

ecpg, the program which pgsanity depends on, chokes on a unicode BOM (https://en.wikipedia.org/wiki/Byte_order_mark). Pgsanity should strip out unicode BOMs before sending the text off to ecpg.

[jayvdb]

At least for file opens, https://github.com/timrburnham/bom_open/ might be a nice way to solve the problem. Note that we've fixed a few bugs since the last release, so it would be worth waiting until the next release is cut, which should be soon.