Add a plugin for querying date fields against date intervals or instants.

The interval syntax is similar to that of NumericQuery.

Example: beet ls 'added:T2008..2010'
convert: fix transcode on windows (#519)
changelog for #519
Web API handles multiple ids
JSON API documentation
Test and fix web /item/query/<query>
Fix typos in web doc
Remove `pyshared` path from coverage

Ubuntu uses /usr/share/pyshared/ to install some packages
Include beetsplug in coverage report
Fix #522: treat copy/move args as dirs and process items accordingly
changelog/thanks for #522
gitignore coverage ouput
silence a ReST complaint
Merge pull request #523 from geigerzaehler/plugin_coverage

Include beetsplug in coverage report
a bit more documentation for --config
tiny PEP8 fixes
Merge branch 'master' of github.com:sampsyo/beets
log errors, don't crash, when calling `convert`
Add reference url in docs
update list of external plugins