fix #1135
remove str decoding as input sources are unicode
Merge pull request #1136 from Kraymer/lyrics-unicode

lyrics: fix #1135 UnicodeEncodeError
Changelog for #1135/#1136
Docs warning about requests dependency (#1136)
lyrics: Handle requests exceptions (#1136)
smartplaylist: Respect sort terms in queries.
Remove unused dbcore import.
Merge pull request #1138 from djl/smartplaylistsort

smartplaylist: Respect sort terms in queries.
Accuracy in variable naming (#1138)

That's a Query object, not a string.
Changelog for #1138/#1137
lyrics: add sources to google CSE
fix writing typos
Merge pull request #1140 from Kraymer/me_gusta_letras

lyrics: add brazilian/hispanic sources to google CSE
Added an option for the import command to print the names of the files to import instead actually importing them.
Some refactoring for better code structure
Added an interface for plugins to filter imported files
Did some changes to use the latest beets source with the enumerate-only option and the file filter.
Some changes for the code structure
Added the regexfilefilter plugin
Some changes to meet the flake8 rules