add .bowerrc
add s3Region attr to directive

The normal behavour was to always use .s3. but when using other regions
the cors preflight was failing because of a rediect. Better to set the
s3 region prefix as an option. Defaults to .s3. which is
us-east-1/standard.
Merge branch 'master' of github.com:whyvez/ng-s3upload