fix(Angular.js): handle duplicate params in parseKeyValue/toKeyValue

parseKeyValue and toKeyValue can now handle duplicate values in the query.
```
?x=1&x=2 <-> {x:[1,2]}
```

The algorithm looks like:
    1)parseKeyValue looks for presence of obj[key]
    2)detects and replaces obj[key] with [obj[key],val]
    3)then pushes more duplicates if necessary
    4)toKeyValue decodes array correctly
    5)(not changed)$location.search({param: 'key'}) still replaces if necessary
    6)(not changed)$location.search({param: ['key1', 'key2']}) sets the url with duplicates

BREAKING CHANGE: Before this change:
parseKeyValue only took the last key overwriting all the previous keys
toKeyValue joined the keys together in a comma delimited string.
This was deemed buggy behavior. If your server relied on this behavior
then either the server should be fixed or a simple serialization of
the array should be done on the client before passing it to $location.