Commit Julienne code and applications.

[ldhulipala]

Main changes:

• Require c++14 (c++1y works as well). Necessary for automatic return type deduction in edgeMap_utils.h
• Add support for vertexSubsets where vertices have an associated data value. type_traits lets us provided an implementation identical to the existing vertexSubset implementation when data = pbbs::empty.
• Add new edgeMaps: edgeMapFilter (count/pack-out neighbors satisfying a predicate) and edgeMapSparse_no_filter (optimized version of edgeMapSparse which writes proportional to the output size)
• Add applications and bucketing implementation from Julienne in apps/bucketing/

Implementation changes:

• Use type_traits ("gen" functions in edgeMap_utils.h) to inline code that writes to a different type of output based on the type of the data.
• Add a "par" flag (default to true) to decode/decodeWgh. This lets us decode sequentially even for -pd codes if necessary.

All existing codes compile without any modifications.

I tested BFS, Components and PageRank with these changes applied vs. the current master and saw no regressions.