t-SNE plot for NMF group

[naikai]

Add t-SNE plot next to NMF identified group results so that user can quickly get a sense of how the results look like

[naikai]

http://shiny.rstudio.com/articles/action-buttons.html

Pattern 3 - Dueling buttons
To build several action buttons that control the same object, combine observeEvent() calls with reactiveValues().

[naikai]

Now needs to implement this

https://plot.ly/r/shiny-coupled-events/

So that we can select samples from the datatable, color samples on the scatter plot.

Also, select (box select) sample on the scatter plot, highlights the corresponding samples in the datatable

[naikai]

Done.

Implemented by using ggplot + ggplotly since plot_ly(type = 'scattergl') still has problem.
Already report an issue to plotly package : #624
It shouldn't be a problem to useggplot for now since most of the time we get less than 1000 samples, but we will definitely need to fix it for gene-gene scatter plot.