Streaming edits

[mafrosis]

As a power user, I want to do:

> jira ls --filter 'label = bacon' --fields key,fix_version
KEY-1    0.1
KEY-2    0.1
KEY-5    null

> jira ls --filter 'label = bacon' --fields key,fix_version | grep 0.1 | jira edit --blah=bacon
KEY-1 blah=bacon
KEY-2 blah=bacon

A pretty contrived example, but the point is that the user can replace grep with any sequence of piped commands they choose. The output fields must configurable via --fields, and edit should accept any old stream of garbage with assumption that first word on each line is a Jira issue key.