Do not output colorized config when environment does not support it

[cfunkhouser]

Currently, regardless of the COLOR / NOCOLOR environment settings, the output of restish api show $API is output in color. This is quite inconvenient when piping the output to other programs which are unable to process the ANSI color codes. In my case, this specifically breaks piping the output into jq.

For example, with the current release:

$ restish api show default | jq '.profiles.default.headers | keys[]'
jq: parse error: Invalid numeric literal at line 1, column 2

With this fix included:

$ restish api show mc | jq '.profiles.default.headers | keys[]'
"authorization"