Updating PR Guidelines

[lalitb]

Trying to update existing PR guidelines to ensure smoother ( and probably faster ) merge process:

• With current small number of Approvers ( and their distribution across different companies ), making number of required approvals ( from different company ) as 1 ( from existing 2 ). We can review this after course of time once we have good distribution.
• Requirement for Updating the changelog (CHANGELOG.md) for non-trivial changes.
• Handling lots of discussions in given PR.

[codecov]

Codecov Report

Merging #413 (cad6811) into master (26dbde3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #413   +/-   ##
=======================================
  Coverage   94.77%   94.77%           
=======================================
  Files         175      175           
  Lines        7591     7591           
=======================================
  Hits         7194     7194           
  Misses        397      397