Added Coverage File Format

[miry]

Added ability to customise the file formats that supported by Shields.io.

[coveralls]

Coverage remained the same at 100.0% when pulling f76bbb8 on miry:patch-1 into 9ab241d on aterris:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9ee31b2 on miry:patch-1 into 9ab241d on aterris:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 359a3ed on miry:patch-1 into 9ab241d on aterris:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 3045022 on miry:patch-1 into 9ab241d on aterris:master.

[coveralls]

Coverage remained the same at 100.0% when pulling bc9d97d on miry:patch-1 into 9ab241d on aterris:master.

[shime]

Thanks Michael, for adding this patch. I would love to see this merged, since Github doesn't support linking to SVG files from a README since that's considered a security vulnerability by them.