feat($compile): Add support for ng-attr with camelcased attributes

- Modify $compile to handle camelcased attributes only with ng-attr to
  support SVG fully

- Change to svg to make clear it works

- Ensure the elements and attributes used are valid SVG elements & attributes

- Modify in attempt to use attribute IE is happy with

- Add specific SVG check for IE

- Fix incorrect attribute value used

Modification to re-run tests

- Break up line for jshint

- Fix codestyle

- Replace with prefix regexp

- Added more test cases to catch prefix regexp

- Add documentation in the guide on using underscores