Docker_image.rst: remove pip install instruction

[vipuldcoder]

pip install is unnecessary in Docker Image docs.

Fixes #486

[newbazz]

Please read the commit guide lines and change the commit message accordingly.

[stellargo]

Mention file changed in title and add a commit body :)
http://api.coala.io/en/latest/Developers/Writing_Good_Commits.html

[yukiisbored]

Hello,

Please read the commit guidelines (coala.io/commit) and change your commit message.

For information on how to change your commit message, refer to coala.io/rebase.

[neelanshsahai]

unack a448fdf
@vipuldcoder it would be better if your shortlog and the commit body are visible and same in both, the conversation as well as the commits section 👍

[yukiisbored]

@neelanshsahai You don't need to unack just to request changes, use GitHub's feature or just make it a comment.
Of course, unack is used when you disagree that this is acceptable and has been ack'd by someone else.

[prashant0598]

@vipuldcoder Pls squash ur commits Refer:https://api.coala.io/en/latest/Developers/Git_Basics.html
& Follow Commit guidelines as already mentioned Refer:
http://api.coala.io/en/latest/Developers/Writing_Good_Commits.html

[yukiisbored]

@vipuldcoder ugh, the dreaded merge commit.

Anyway to fix this, please do the following:

1. Create a new branch based of this branch you're using for this PR. git checkout -b <whatever you wanna call>
2. Make sure you've fetched/pulled the latest master branch. git pull <whatever your remote to the coala repo is> master
3. Checkout to master. git checkout master
4. Delete the branch you're using for this PR. DON'T WORRY, GitHub only cares about the branch name, we'll fix it later. git branch -D <the branch name>
5. Create a new branch based of the latest master with the same name as you're using for this PR. git checkout -b <whatever the name is>
6. Cherrypick your commit to your new branch. git cherry-pick <the commit hash of whatever you did>
7. Do a force push to your fork. git push -f -u <whatever your fork remote is> <whatever your branch name is>

[neelanshsahai]

@vipuldcoder please rectify your PR asap
Squashing the commits and updating your Shortlog and Commit Body would be great. 👍

[jayvdb]

@gitmate-bot rebase

[gitmate-bot]

Hey! I'm GitMate.io! This pull request is being rebased automatically. Please DO NOT push while rebase is in progress or your changes would be lost permanently ⚠️

[gitmate-bot]

Automated rebase with GitMate.io was successful! 🎉

[jayvdb]

Please fix your commit message to abide by http://coala.io/commit .
Otherwise we will close this PR as abandoned.