bug fix : it does not work, when raw_get is called with only entities.

for instance, Member.raw_get(["test user", "challenges"]) sends request with the url http://cs-api-sandbox.herokuapp.com/v1/members?testuser/challenges. because in raw_get method ["test user", "challenges"] is regarded as params, not entities.
implements '/account/challenges' page.
bug fix
Merge pull request #19 from aproxacs/cs-2050-port-my-challenges

Cs 2050 New Rails Site - Port My Challenges