Rename 'src' to 'lib' to match every other Ruby project on earth.

diff --git a/src/errors.rb b/lib/errors.rb
similarity index 100%
rename from src/errors.rb
rename to lib/errors.rb

diff --git a/src/exit_codes.rb b/lib/exit_codes.rb
similarity index 100%
rename from src/exit_codes.rb
rename to lib/exit_codes.rb

diff --git a/src/filesystem.rb b/lib/filesystem.rb
similarity index 100%
rename from src/filesystem.rb
rename to lib/filesystem.rb

diff --git a/src/mailstore.rb b/lib/mailstore.rb
similarity index 100%
rename from src/mailstore.rb
rename to lib/mailstore.rb

diff --git a/src/plugin.rb b/lib/plugin.rb
similarity index 100%
rename from src/plugin.rb
rename to lib/plugin.rb

diff --git a/src/plugins/dovecot_mailstore.rb b/lib/plugins/dovecot_mailstore.rb
similarity index 100%
rename from src/plugins/dovecot_mailstore.rb
rename to lib/plugins/dovecot_mailstore.rb

diff --git a/src/plugins/roundcube_db.rb b/lib/plugins/roundcube_db.rb
similarity index 100%
rename from src/plugins/roundcube_db.rb
rename to lib/plugins/roundcube_db.rb

diff --git a/src/postfixadmin_db.rb b/lib/postfixadmin_db.rb
similarity index 100%
rename from src/postfixadmin_db.rb
rename to lib/postfixadmin_db.rb