increase hardcoded pregelix framesize (tmp fix)

@anbangx @Nan-Zhang @JavierJia @Elmira88 
Hi all, if you're planning on running our pipeline on decently sized data and will be doing a lot of merging, you're going to need to make adjustments to the pregelix's hard-coded bufferCache pageSize.  Yingyi is working on a way to configure this, but for now just make a change similar to what  you see in the diff. 

This will solve problems that look like:
```java
Caused by: edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException: Space required for record (137070) larger than maximum acceptable size (131059)
```