New formula: ttylog

Hi guys! :)

ttylog is a serial port logger, very useful to read serial communications from Arduino, for example.

In `CMakeLists.txt`, the `install target destination` builds everything in `#{prefix}/sbin` so I've made a little [patch](https://gist.github.com/ladislas/a3189d4b5a4304b6a115) to build in `#{prefix}/bin`

It's my first formula, so I may have made mistakes. Please tell me everything I need to change :)
`std_cmake_args` is already defined: https://github.com/Homebrew/homebrew/blob/8e778b916d5a61aa231d1ce94b534eb3595b5039/Library/Homebrew/formula.rb#L326-L334