Close #17 and Close #16

Introduces CMDARG_ERROR_BEHAVIOR. Adds some more tests. Introduces new
behavior for hash validators (see README). Fixes a few odds and ends.

README.md

@@ -100,6 +100,14 @@ For example, this is a valid validator:
 
     cmdarg 'x' 'x-option' 'some opt' '' "grep -E '^[0-9]+$'"
 
+There is an exception to this form, and that is for hash arguments (e.g. 'x:{}'). In this instance, the key for the argument (e.g. -x key=value) is to be considered a part of the value, and the user may want to validate this as well as the value. In this instance, when calling a validator against a hash argument, the validator will receive a second argument, which is the key of the hash being validated. For example:
+
+    # When we receive
+    cmdarg 'x:{}' 'something' 'something' my_validator
+    cmdarg_parse -x hashkey=hashvalue
+    # ... we will call
+    my_validator hashvalue hashkey
+
 cmdarg_info
 ===========
 
@@ -239,6 +247,21 @@ The short options for all specified arguments in cmdarg are kept in a hash ${CMD
 
 For examples of this behavior, please see ./tests/test_helpers.sh, the "shunittest_test_describe_and_usage_helper" function.
 
+Controlling cmdarg's behavior on error
+======================================
+
+By default, whenever something happens that cmdarg doesn't like, it will 'return 1' up the stack to the caller. This is different from the old behavior in v1.0, which would 'exit 1'. You can control cmdarg's error behavior by setting the CMDARG_ERROR_BEHAVIOR variable to the function/builtin you want called whenever an error is encountered.
+
+To get the old v1.0 behavior back, you can, before calling any cmdarg functions:
+
+    CMDARG_ERROR_BEHAVIOR=exit
+
+If you want cmdarg to call some function of your own when it encounters an error, you could:
+
+    CMDARG_ERROR_BEHAVIOR=my_error_function
+
+CMDARG_ERROR_BEHAVIOR is treated as a function call (e.g. return or exit) with one argument, the value to return. You will be given no more context regarding the error (and, in fact, you should not expect this to be called unless a fatal error has been encountered, whether during setup or parsing).
+
 getopt vs getopts
 =================