bugfix: convert ints to strings before write

[tgolly]

Minor bugfix.

When using "--output text", if the value returned is an integer, this error is returned:

# aws ec2 describe-volumes --volume-ids $VOL_ID --query 'Volumes[0].Size' --output json
10
# aws ec2 describe-volumes --volume-ids $VOL_ID --query 'Volumes[0].Size' --output text

argument 1 must be string or read-only character buffer, not int

This patch ensures the value is converted to a string before .write. After patch:

# aws ec2 describe-volumes --volume-ids $VOL_ID --query 'Volumes[0].Size' --output text
10

[jamesls]

Thanks for the PR. Just needs a few unit tests that demonstrate the bugfix. These should be pretty small so I'll go ahead and write them real quick before merging in.

[jamesls]

Merged, thanks!