[WIP] Initial implimentation of a volume slider for the audio element.
Finished work on volume control.

It is bound correctly and styled.

Ready for review.
Fixed layout bugs

Fixed height bug in IE due to font-size of other icons.

Fixed, left border bug.
Merge pull request #59 from QutBioacoustics/volume-control

feat(playback) Volume slider for the audio element. Closes#56