Modify ofVbo bind method to allow 2d vertices

Currently ofVbo bind method always sets number of components in vertex position data to 3. Fix to set number of components to either 2 or 3 based on numCoords argument to setVertexData call when passing in pointer to float array of vertices.
Merge pull request #2736 from jayvius/vbo_fix

Modify ofVbo bind method to allow 2d vertices