Uproot

Added

* Writing `TH1`, `TH2`, `TH3`, `TProfile`, and `TProfile2D`.
* Memory size units as strings, like `"1 GB"`, particularly in **entrysteps** (e.g. `for data in tree.iterate(entrysteps="1 GB")`). (Issue 285)
* `tree.mempartitions` implements memory-sized partitions, like clusters but targeting a memory size.
* Memory size units can be used in all arguments that specify a number of bytes, such as `limitbytes`, `chunkbytes` in `ArrayCache` and `uproot.open` for remote files.
* HTTP and XRootD source options can now be passed simply into `uproot.open("http://remote/file.root", limitbytes="1 GB")`.
* Fixed error in **entrysteps** (Issue 286).
* Fixed some documentation.
* Fixed branch selection with a boolean function.

XRootDSource.defaults['parallel'] = False because pyxrootd asynchronous mode deadlocks too easily.

PR 280 (fixes for LPC HATS), specifically better handling of lazy arrays, as well as a bug in reading from writable files (chunked file source missing an argument).

Replaced the custom `LazyArray` class with `awkward.ChunkedArrays` of `awkward.VirtualArrays`.

Updated the minimum versions: awkward 0.10.0+ and uproot-methods 0.6.0+.

Fixes 274, a bug when reading `asgenobj` branches through `uproot.iterate`.

PR 269: adds the ability to write 2 and 3 dimensional histograms to ROOT files.

PR 270: makes XRootDSource safe to use in multiprocessing.