Configurable list of patterns which will be ignored when pruning empty directories.

* util.prune_dirs modified to accept glob patterns as clutter to determine emptiness.
* config option, 'clutter' (a list of filenames/glob patterns)
* ImportTask.prune passes this option's value to prune_dirs.
Merge pull request #93 from steinitzu/prune-dirs-clutter

Customizeable clutter when pruning directories
changelog, docs, and style tweaks for #93
Adds support for Replay Gain tags on MP4 files

 * Stores Replay Gain info in MP4 files using the format
   '---:com.apple.iTunes:replaygain_*' which is used by FB2K
Fixes a typo. Whoops.
Ugh, more typos.
Merge pull request #94 from daveisadork/m4a-replaygain

Adds support for Replay Gain tags on MP4 files
changelog for #94
correct changelog credits for @mrmachine
echonest_tempo: skip when missing artist or title
Merge pull request #92 from pscn/master

lastgenre improvements
Python style and legibility cleanup for #92
changelog for #92
remove verbose option (#92)

The lastgenre command should always log what it's doing so the user can see
the progress being made. If you really don't want any output, just pipe to
/dev/null.
simplify configuration handling (#92)
canonicalize original genre (#92)
lastgenre: "auto" config option
collapse separate album and item paths (#92)

Should reduce copypasta overhead significantly.
Override implicit OR explicit default if `require=True` for `input_option()`.
Merge pull request #95 from mrmachine/require-overrides-default

Override implicit OR explicit default if `require=True` for `input_optio...