Created main source file

Created hw04.asm to hold the main source for the project.

Coded an initial implementation in hw04.asm.
Added project header

Added a header describing the project to the top of the source file.
Updated .gitignore

Added Vim temporary files to the git ignore list.
Added COUNT branch

Added a branch to increment the value of R7, as adding the result
of R0 (value) AND R1 (mask) doesn't work, as the reslt of the AND
is not #1, but rather some number with either 1 or 0 bits set.

Thus, if the result of the AND is positive, then we want to branch
out of the normal loop, increment R7, and branch back to the top
of the main loop.
Added counting branch

Added a branch to increment R7 whenever a set bit is found.

Removed extraneous spacing from the source file.
Updated README

Updated the README with information on how to build and run projects
using the LC3 tools.
Merge branch 'develop'

Initial stable build.

There may be bugs, but this version will build and run without
errors or crashes.