Disable coloring if stdout is not a terminal

Signed-off-by: Solomon Hykes <solomon@docker.com>

This allows piping and redirecting the output of `pulls` without mixing
in term control characters garbage.
remove filters from issues
Merge pull request #107 from shykes/autocolor
Show contributors next to assignee when listing all PRs
Merge branch 'contributors'
Merge pull request #112 from dotcloud/remove_filters2
Use email and not github name
Merge pull request #115 from crosbymichael/only-email

Use email and not github name
general cleanup + much faster
Merge pull request #116 from dotcloud/more_filters_cleanup

general cleanup + much faster
add initial --maintainer
Merge pull request #117 from dotcloud/maintainer
fix steal
Merge pull request #118 from dotcloud/fix_steal
`pulls send`: send a new pull request or overwrite an existing one

Signed-Off-By: Solomon Hykes <s@docker.com>
Show SHA of pull request to easier spot changes

Signed-Off-By: Solomon Hykes <s@docker.com>
Merge branch 'pr-119' into approved
Merge branch 'pr-120' into approved