[Bug Report] Bot won't change channels when "stayinchannel = true" and nothing playing

**Describe the bug**
The bot will not change channels when "stayinchannel = true" and nothing is currently playing/in queue. The message "You must be listening in {{channel_name}} to use that!" is displayed instead.

**To Reproduce**
Steps to reproduce the behavior:
1. Set "stayinchannel" is set to "true" in config.txt and save.
2. Start the bot, or restart if it was already running.
3. Join a voice channel.
4. Issue a !play {{song}} command to have the bot join the voice channel.
5. Wait for the song to finish, or issue the !stop command.
6. Join a different voice channel from the bot.
7. Issue a !play {{song}} command and observe the aforementioned error message. The bot does not move channels despite nothing currently playing.

**Expected behavior**
When no songs are playing/the bot is not in use, it would be desirable for the bot to take this into consideration and change channels to the new requester's voice channel. This grants users peace and quiet (no join/part voice channel sounds during idle time between songs), while continuing to allow the the bot to move freely.

**Version Info (please complete the following information):**
- Operating System: Windows Server 2016 x64
- JMusicBot Version: 0.2.3

**Additional context**
I realize this is partially covered with an upcoming command for DJs, but this is specifically for scenarios where the bot is idling in a voice channel but not playing anything at all. May also be more appropriate as a feature request than a bug, so please forgive the potential miscategorization on my part.

Start by tracing the !play command and the stayinchannel configuration when the bot is idle in a voice channel. Reproduce the listed steps, then verify that a new requester can move the bot when no song is playing while the existing restriction remains when playback is active.

Written by the indexing model from the issue text.