Various small fixes for v1.0.0a5

[emarinier]

• Modified updatedb's wget to write less to stdout.
• Made sure quast uses the specified contig size.
• "continue" -> "break" when considering mash command size
• Changes the directory mash runs from to reduce to length of file paths.

[emarinier]

@ericenns The solution for using shorter relative paths instead of longer absolute paths involves finding the common path of all input files and working from the directory of the common path. There's a bit of extra logic to handle when there's only 1 input file or multiple input files in completely different directories.

[emarinier]

Thanks Aaron. Good catch. It turns out I needed to take the absolute path of any file I try to take the directory name from, because a relative path without a directory (ex: "contigs.fasta") would return an empty string for the dirname and then subprocess would try to run the process from an empty string directory.

[emarinier]

I made one other comment about parallel mash screen (just writing this here again so it's part of a review).

Added in d1071ce