HTTP port can now be overriden through use of "port" environmental
variable.

Prefer messaging "want" over "wanted" in error messages, this is more
idiomatic Golang.

Move away from Go ARMv6 (RPi Zero) and give ARMv7 as a minimum
version for release binaries.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>