Added name.{out,err} files for jobs.

The Mdjob class now automatically sends the job output to the file
'job_name.out' and the error to 'job_name.err'. The 'combine_err_out'
boolean keyword argument allows stdout and stderr to be combined.

Also added a 'config.py' file for system-wide constants, like the name
of the output file and the standard error file.
Added 'combine_out_err' keyword to qsub in iawful.
Merge pull request #8 from pbugnion/io_redirection

Output now saved to 'job_name.out', error to 'job_name.err'. Additionally, the keyword 'combine_out_err' allows the two files to be merged.

Closes #5.