Merge pull request sleepdefic1t#12 from sleepdefic1t/develop

# v.0.3.1

**Changes since [v0.2.1](https://github.com/sleepdefic1t/BIP66/releases/tag/0.2.1)**
- drops vectors for arrays (bye bye dynamic allocation).
- reworks logic to lower complexity.
- improves project layout.
- moves builds fully out of source.
- moves Google Test out of source and drops the submodule method.
- updates test vectors to be const c arrays.

## Installation

### Arduino IDE

Download BIP66 from the Arduino IDE Library manager, or clone/download this repo and place it in the Arduino Libraries directory.  (_e.g. `~Documents/Arduino/libraries`_)
1) Open the `BIP66.ino` sketch in the `examples/BIP66` folder.  
2) Select your board from the Arduino IDE
3) Upload the sketch.

### PlatformIO

**Building the Library**
-    `pio run`

**Building the Library with Tests**
-    `pio run -t test/`

**Uploading and Running Tests**
-    `pio run -t test/ -e esp32 -t upload`

### CMake

Operating System builds like Linux, macOS, and Windows use CMake to build this BIP66 library.  
This build should be done out of source.

**Building the Library**
1) `mkdir build && cd build`
2) `cmake ..`
3) `cmake --build .`

**Building and Run Tests**
1) `mkdir build && cd build`
2) `cmake -DUNIT_TEST=ON ..`
3) `cmake --build .`
4) `./test/bip66_tests`

exclude tests from export

release: 0.2.0

Update library.json