Updating Installation Instructions

Added the recommended way of adding composer requirements to your projects.
The new tooling in composer can now choose the proper version and bind it correctly by using "~" and not `*`  ranges.
Ranges with `*` are more costly and resource heavy for composer and should be avoided.
Typos

Since i cannot type, i fixed some typos.
Merge pull request #3 from rdohms/patch-1

Updating Installation Instructions