Previously we were only loading "official" checkers that had been added
to syntastic. Now we load any checker that is in the right directory.
This allows anyone to add custom checkers to any filetype that uses
`SyntasticLoadChecker()`
It will compile all *.java files in the pwd and apply the errorformat string
from quickfix.txt
Interesting additional features would be:
* @argument files
* setting the pwd for javac
* perform only a syntax check (javac currently always builds class files)
