Add kubectx as an arkade get option

Changelog for 0.3.7:

• PR #124 tool: add kubectx by @tuananh
• PR #126 Add nats connector app by @viveksyngh
• PR #97 Download (get) commands and CLIs by @alexellis

Commits
9c1979f Fix help message for arkade get by @alexellis
18c2522 Add kubectx as a tool by @tuananh
211b513 Add info command for nats connector by @viveksyngh
52847c7 Add nats connector app by @viveksyngh
78f6338 Document "arkade get" by @alexellis
4efd6d7 Add "get" command by @alexellis
0aef8d2 Update headings by @alexellis
8ebbc9a Remove k3sup reference by @alexellis
3246434 Update .gitignore by @alexellis

Generated by Derek