Gofmt, remove network card, examples centos7, fix gopkg, fixing CPU_limit

[remijouannet]

Hello,

Multiple things in this PR, sorry if this is too big

• Fix Gopkg.toml, apparently the syntax of version wasn't right and I had a build error about a commit that didn't exist anymore (i'm guessing the commit was squash from a PR)

• add gofmt to build.sh, the majority of change in this PR came from this

• add the configurable step "remove_network_card" that remove all network cards from the instance after shutdown and before snapshot/template

• add build instruction to README.md

• CPU_limit set to -1 by default, otherwise 0 is set and the virtual machine freeze (fixing VMware console glitches #136, v2.0 - installations hang during "Setup" #119)

• add a examples for building a centos7 template

[segator]

remove_network_card --> Tested OK
CPU_limit set to -1 by default, otherwise 0 is set and the virtual machine freeze: I had the freeze problem and now ok.

Are you going to integrate it? I'm planing to use this plugin for my development automated procceses from jenkins.

[mkuzmin]

thank you for the contribution. This PR is so huge, and so many things are mixed together, so I cannot merge all them together. Small PRs which are specific and independent, are much easier to handle.

But still, there are several changes I'd happy to apply.

Fix Gopkg.toml

cannot reproduce. A few days ago I've updated the code to dep v0.5. This may help.

add gofmt to build.sh

great idea. build script (especially at CI server) should report violations and break the build, not fixing it automatically. like golang/go#24230 (comment)

add the configurable step "remove_network_card"

this is a controversial item. 1) I don't understand a use case 2) we're going to rework network parameters - make it a list of maps, with multiple settings for each card.
let's discuss use cases in a separate issue.

add build instruction to README.md

good point! I usually use docker-compose run build - it returns an exit code.

CPU_limit set to -1 by default,

I've fixed it in more generic way - inside the driver

add a examples for building a centos7 template

I have no experience with CentOS yet and need to play with it. please open this separately.

Sorry for closing the PR

[remijouannet]

Yeah sorry, that PR was a bit messy i will rework that