Introduce TTS-API.com service support

Basically follows the same pattern as Google, but with only one voice.
Merge branch 'develop' into add/tts-api-com

Resurrects this ancient branch to add support for TTS-API.com.

Conflicts:
	addon/awesometts/service/__init__.py
	awesometts/__init__.py

Manually moved:
	addon/awesometts/service/ttsapicom.py
Update TTS-API.com description

Switches this to read "(English only)", similar to the other services.
Port TTS-API.com to use self.normalize()

This brings the normalization up-to-standard with the other services.
Implement long phrase support for TTS-API.com

Switches the net_download call to make use of the split functionality
now available.
Enforce minimum size on MP3s from TTS-API.com

Sets this to 256, unlike the others that are at 1024.
Special handling for single-item dropdowns

For services that have an option with only one available value, disable
the dropdown box and do not display a "[default]" string with it.
TTS-API.com service page on website

Adds documentation so the "Help" button has somewhere to go.
Add TTS-API.com to README

Lists this with the other services.
Mention other projects on Contribute page

Plugs the other projects that AwesomeTTS depends on to exist as part of
the Contribute page.
Increase bottom padding on article container

This provides more of a visual separation between the article content
and the footer (at all viewport sizes).
Merge branch 'add/tts-api-com' into develop

Adds support for the TTS-API.com service.