Copied Addition.java from week34
Altered Addisjon.java to use floats instead of ints (Week 34, Task 1)
Implemented class calculating sum, product, difference and quotient of two decimals (Week 34, Task 2)
Stubbed out the LawnMower class
Stubbed out UnitTests class and added a makefile

I'm giving test-driven development a shot.

This commit was a huge pain in the a** to figure out. I've learned
that:

* The classpath needs to be set explicitly either in the environment
  or when calling javac or java, and it must point to the actual jar
  file. It seems that Javac doesn't look in /usr/share/java by default.

* It's not possible to write "import org.junit". I assume this is
  because import-statements must refer to classes, not packages.

* JUnit 3 and Junit 4 are very different. Googling for snippets left
  me more confused than I already were.