Fix build bug and a compiler warnings.

[pelesh]

Description

• Fix CMake bug preventing code to build on Linux/MacOS
• Fix compiler warnings due to implicit conversion from unsigned to signed integer.

Closes #(issue)

Proposed changes

Needed quick fixes for #151

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.

Further comments

[lukelowry]

I did not receive compiler warnings without these changes, but I trust these changes are generally needed. Thank you for the formatting adjustments as well.

[lukelowry]

Merged. Thank you