Update README to include infinite precision (#470)

Fixes #119

Added infinite precision as a feature in README.md and in ApplicationArchitecture.md

How changes were validated:
Manual preview of README and ApplicationArchitecture.md

README.md

@@ -16,6 +16,9 @@ Calculator ships regularly with new features and bug fixes. You can get the late
 - Calculation history and memory capabilities.
 - Conversion between many units of measurement.
 - Currency conversion based on data retrieved from [Bing](https://www.bing.com).
+- [Infinite precision](https://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic) for basic
+  arithmetic operations (addition, subtraction, multiplication, division) so that calculations
+  never lose precision.
 
 ## Getting started
 Prerequisites:

docs/ApplicationArchitecture.md

@@ -153,7 +153,9 @@ The CalcEngine contains the logic for interpreting and performing operations acc
 
 ### RatPack
 
-The RatPack (short for Rational Pack) is the core of the Calculator model and contains the logic for performing its mathematical operations. The interface to this layer is defined in [ratpak.h][ratpak.h].
+The RatPack (short for Rational Pack) is the core of the Calculator model and contains the logic for
+performing its mathematical operations (using [infinite precision][Infinite Precision] arithmetic
+instead of regular floating point arithmetic). The interface to this layer is defined in [ratpak.h][ratpak.h].
 
 [References]:####################################################################################################