Updating the docs to mention c++17

Author: andrewdavidsmith

README.md

@@ -1,20 +1,22 @@
 # The smithlab_cpp library
 
-This library contains code that has been used in the Smith lab for
-several years, and that we now depend on for several of our data
-analysis tools. Many of those tools use older versions of this source
-code in subdirectories of other repos.
+This library contains code that has been used in the Smith lab for too
+many years, and that we depend on for several of our data analysis
+tools. Many of those tools use older versions of this source code in
+subdirectories of other repos.
 
 ## Requirements
 
-- A C++ compiler that knows C++11. The GNU `g++` compiler works well
-  for this after version 5.3.
-- The GNU Scientific Library, GSL, which is likely already on your
-  system, or easily installed through a package manager.
+- A C++ compiler that knows C++17. The GNU `g++` compiler works well
+  for this after version GCC9, and the default since GCC11. You can
+  get this from apt, conda and brew, but beware on macos where it's
+  not really installed by default even though it pretends to be.
 - The [zlib library](https://zlib.net), which we use for I/O of files
-  in gzip format. You likely have this on your system.
+  in gzip format. You likely have this on your system. You can get
+  this from apt, conda and brew, and it's likely installed already.
 - Optional: The [HTSLib library](http://htslib.org), which we use for
-  I/O of SAM and BAM format files.
+  I/O of SAM and BAM format files. You can get this from apt, conda
+  and brew.
 
 ## Building and installing the smithlab_cpp library
 
@@ -55,7 +57,7 @@ use it the way it has been used from 2010-2019, then you can use the
 `Makefile` in this repo without running the `./configure` script:
 ```
 $ make OptionParser.o
-g++ -Wall -std=c++11 -c -o OptionParser.o OptionParser.cpp
+g++ -Wall -std=c++17 -c -o OptionParser.o OptionParser.cpp
 ```
 Note: if you run the `./configure` script it will overwrite the
 `Makefile` indicated above. If that happens, just get a new one.  The
@@ -72,7 +74,7 @@ result should be less total code overall in smithlab_cpp.
 - `QualityScore.*pp` likely should be removed, as we only use
   sequencing quality scores in specific places, and in those places
   have chosen to re-implement anything that would be here.
-- `smithlab_os.* Any use of character arrays should be replaced with
+- `smithlab_os.*` Any use of character arrays should be replaced with
   strings for filenames. Implementation of many functions in the cpp
   file is sloppy.
 - `smithlab_utils.*pp`: lots to replace here. Many functions seem