pants: upgrade to v1.2.1 (from v1.2.1rc0) (#291)
pants: upgrade to v1.2.1 (from v1.2.1rc0) (#291)

The main change fixed by moving from the rc0 of 1.2.1 to the final 1.2.1 is that zinc name hashing is enabled by default. In order to use that feature though, any source files generting empty[1] output must be removed from the tree since zinc gets confused.

[1] "empty" meaning nothing but imports, so no classes, traits, etc.
(sapling split of dd4d933584acbd72b0c23a0e84cecc6c8c637068)

foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio