Merge pull request #96 from LI-HE/master

resloved the $digest issue
show national flag in challenge list
code formatting #1
Merge pull request #97 from LI-HE/master

changed home video from iframe to pop up
Merge pull request #98 from LI-HE/master

minor css change for home page and deleted unecessary file
Load challenges made by other users
Revert "Load challenges made by other users"

This reverts commit 13214f8607ed14f897e13d80c383bc2c8a666558.
Merge pull request #29 from ChrisBoesch/master

update