fix: fix suspend issue on some distributions

Fix an issue (#3) on some
distributions, most notably Ubuntu, where the charging threshold would
not persist after the system went into suspend.

This also updates the documentation and refactors the code to handle
errors better.

README.md

@@ -1,25 +1,32 @@
 # `bat`
 
-```
-                                      bat
+```                                     bat(1)
 NAME
-    bat - battery management utility for Linux laptops
+    bat -- battery management utility for Linux laptops 
 
 SYNOPSIS
-    bat [OPTION]
+    bat [-chprst] [-t num]
 
 DESCRIPTION
-    -c, --capacity      print the current battery level
-    -h, --help          print this help document
-    -p, --persist       persist the current charging threshold setting between
-                        restarts (requires superuser permissions)
-    -r, --reset         prevents the charging threshold from persisting between
-                        restarts
-    -s, --status        print charging status
-    -t, --threshold     print the current charging threshold limit
-                        specify a value between 1 and 100 to set a new threshold
-                        (the latter requires superuser permissions)
-                        e.g. bat --threshold 80
+    The following options are available:
+
+    -c, --capacity  
+        Print the current battery level.
+    -h, --help      
+        Print this help document.
+    -p, --persist   
+        Persist the current threshold between restarts.
+    -r, --reset    
+        Undoes the persistence setting of the charging threshold between 
+        restarts.
+    -s, --status
+        Print the charging status.
+    -t, --threshold num
+        Print the current charging threshold limit.
+        If num is specified, which should be a value between 1 and 100, this
+        will set a new charging threshold limit.
+    -v, --version
+        Display version information and exit.
 ```
 
 ## About
@@ -30,9 +37,11 @@ The goal is to replicate the functionality of the [ASUS Battery Health Charging]
 
 This has only shown to work on ASUS laptops. For Dell systems, see [smbios-utils](https://github.com/dell/libsmbios), particularly the `smbios-battery-ctl` command, or install it using your package manager. For other manufacturers there is also [TLP](https://linrunner.de/tlp/).
 
+There have also been some [problems setting the charging threshold inside of a virtual machine](https://github.com/leveson/bat/issues/3#issuecomment-858581495).
+
 ## Installation
 
-Precompiled binaries (Linux x86-64) are available from the [GitHub releases page](https://github.com/leveson/bat/releases), the latest of which can be downloaded from [here](https://github.com/leveson/bat/releases/download/0.5/bat).
+Precompiled binaries (Linux x86-64) are available from the [GitHub releases page](https://github.com/leveson/bat/releases), the latest of which can be downloaded from [here](https://github.com/leveson/bat/releases/download/0.6/bat).
 
 After downloading the binary, give it permission to execute on your system by running the following command. For example, assuming the binary is located in the user's Downloads folder: