go 1.5 not building

[sebgoa]

just to confirm, we are now using go 1.6, and 1.5 does not work anymore.

travis runs 1.6

we need to update the readme

[kadel]

You should be able to compile Kompose with go 1.5

on go1.5 I can build with cgo disabled it like this:

CGO_ENABLED=0 GO15VENDOREXPERIMENT=1 go build -o kompose -tags experimental ./cli/main

I don't know why, but if I try to build it with cgo it fails on:

# github.com/skippbox/kompose/vendor/github.com/opencontainers/runc/libcontainer/system
cannot load DWARF output from $WORK/github.com/skippbox/kompose/vendor/github.com/opencontainers/runc/libcontainer/system/_obj//_cgo_.o: decoding dwarf section info at offset 0x4: unsupported version 0

With go1.7 I can build it in both cases (with and without cgo).
It looks like that for go1.5 cgo has to be disabled. I don't know why :-( Maybe I'm doing something wrong. I don't know much about go compiler :-(
Maybe @janetkuo has idea?

[ngtuna]

So I made a direct update to README accordingly for both cases. 9cb74ed