hoc2015: update one video thumbnail.
hoc2015: update one video thumbnail.

rvarshney/code-dot-org,pickettd/code-dot-org,pickettd/code-dot-org,rvarshney/code-dot-org,rvarshney/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,rvarshney/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,dillia23/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,rvarshney/code-dot-org,rvarshney/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,dillia23/code-dot-org,rvarshney/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,rvarshney/code-dot-org