add support for bulker

[nsheff]

adding support for bulker would be sweet. here's what we'd need to do:

• pipeline interface adds bulker_crate attribute
• on --bulker flag, looper first runs a bulker pull {bulker_crate}
• on --bulker flag, looper prepends bulker run {bulker_crate} to each command

I think that's it...pretty simple...

question: why is this superior to using the divvy bulker templates? well...this automatically works with whatever existing template without requiring a new template.

[nsheff]

right now this is still working with divvy; it is not integrated into looper