Add CONTRIBUTING.md

[bhavin192]

• This makes it easy for someone new to start working on BotKube
• Adds instructions to build BotKube from source code
• Based on
  https://github.com/jaegertracing/jaeger-client-python/blob/master/CONTRIBUTING.md
  which is Apache 2.0 licensed

[PrasadG193]

Add section to run BotKube outside cluster
the steps are:

• Make BotKube binary (we should probably add make rule for that)
• Modify config.yaml placed at project root directory
• Export CONFIG_PATH={path where config.yaml is placed}
• Make sure that correct context is set and you are able to access k8s cluster
• run ./botkube binary

[bhavin192]

@PrasadG193 Thanks, will consider adding that.

[mugdha-adhav]

• To avoid build failures in travis CI, run ./hack/verify-*.sh to check if the code is properly formatted, linted & vendor directory is present.

• And also mention - if the PR is approved, please squash all the commits and rebase with develop for your PR to be merged

[bhavin192]

To avoid build failures in travis CI, run ./hack/verify-*.sh to check if the code is properly formatted, linted & vendor directory is present.

Yes, we should add that, thanks.

if the PR is approved, please squash all the commits and rebase with develop for your PR to be merged

Personally I don't think squashing all the commits every time is a good idea, if you take a look at this PR transtats/transtats#160. It would have been hard to find out which change is done for what reason if we squash all the commits. I like to leave it to the contributor to decide which commits go to the devel branch. If there are small fixing commits we can always ask them to squash those commits into proper commits. Doing this also helps one to find out reason for a change by running git blame filename

[mugdha-adhav]

Personally I don't think squashing all the commits every time is a good idea, if you take a look at this PR transtats/transtats#160. It would have been hard to find out which change is done for what reason if we squash all the commits. I like to leave it to the contributor to decide which commits go to the devel branch. If there are small fixing commits we can always ask them to squash those commits into proper commits. Doing this also helps one to find out reason for a change by running git blame filename

Yes, rather than asking to squash all commits, we can request to squash the unimportant commits.

[bhavin192]

Yes, that makes more sense. We can say something similar

[bhavin192]

@PrasadG193 can you please check the instructions of 'Build and run BotKube locally' once, as I don't have Mattermost/Slack workspace configured with BotKube to test that.

[bhavin192]

This PR depends on #89

[sanketsudake]

@bhavin192 Can you please rebase your branch with develop?

[bhavin192]

@ssudake21 done

[sanketsudake]

Thanks. LGTM

[PrasadG193]

@bhavin192 can you please rebase with develop?

[bhavin192]

@PrasadG193 yes, done :)