Add .gitignore to ignore build directory
Rename HACKING -> HACKING.md
Add "Install on Windows (MinGW)" section
HACKING.md: Fix some new lines
HACKING.md: Improve documentation
Small fixes to the installation file.
More tweaks to INSTALL.md.
Language fixes to the INSTALL file.
Merge pull request #6 from atowers-devs/devel

Added an INSTALL.md with details on building and running atowers on GNU/Linux and Windows.