Fix #8.

Thank you mut0u for pointing otu this bug. And yes, I am using ajoke
exclusively in any java-related programming task, android or
non-android.

As for the double quotes in

#+BEGIN_EXAMPLE
export ajoke_dir="~/ajoke"
#+END_EXAMPLE

they are unnecessary, as is stated in (bash) Shell Parameters. As a
matter of fact, most quotes are unnecessary in variable assignment in
bash scripts, but I have this bad habits of adding them sometimes
while omitting them other times.

README.org: ajoke #8
bin/ajoke-test-drive: ajoke #8

Signed-off-by: Bao Haojun <baohaojun@gmail.com>