[MRG] Update README and fix <pre>...</pre> rendering

[bharatr21]

First off, thanks for the amazing project!

Few things which I had trouble from the README which could benefit many users:

• Remove the $ from the bash commands to make it copy-pastable for users
• Mention Quickstart Guide

[codecov-io]

Codecov Report

Merging #340 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #340   +/-   ##
=======================================
  Coverage   87.64%   87.64%           
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  Files          13       13           
  Lines        1505     1505           
  Branches      348      348           
=======================================
  Hits         1319     1319           
  Misses        129      129           
  Partials       57       57

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[vinayak-mehta]

The $ acts as a hint on where to run those commands, which are not very long. How does the '```bash' help here?

[bharatr21]

@vinayak-mehta as mentioned above, removing the $ makes it easily copy-pastable for users in a bash shell and the '```bash' helps in syntax highlighting bash-specific commands such as cd, if any