Uproot

Fixes issue 340 (PR 343 )
Fixed append - takes a number and not an array/list. Issue 336 (PR 344 )
Fixed extend's behaviour when flush is set to True. (PR 342 )

uproot can now write TTrees containing baskets with flat data!

Example -

import uproot
filename = "example.root"

b = uproot.newbranch(">i4", compression=uproot.LZMA(3))
branchdict = {"intBranch": b}
tree = uproot.newtree(branchdict)
a = [1, 2, 3, 4, 5]
with uproot.recreate(filename, compression=uproot.ZLIB(4)) as f:
f["t"] = tree
f["t"]["intBranch"].newbasket(a)

Adds `TRefArray` (PR 330), in addition to just `TRef` (PR 326).

Fixes 327, a naive regular expression for determining streamer types from TBranch titles.

PRs 319, 320, 243 (redux), 325, and 326.

* Fixed a memory issue (Python garbage collector gets too far behind) related to large basket recovery.
* ROOT now splits the serialization of `std::map`; added handling of split key-value pairs.
* Implemented TRef as a type that can be read from TTrees.

No change in code, but this is the first release to explicitly require awkward<1.0, so that when awkward 1.0 does come to exist, most uproot users won't accidentally upgrade to it. (PR 318)

To get awkward 1.0, users will need to explicitly upgrade to uproot 4.0.