The parser must throw an exception with all the errors encountered

[MrDave1999]

For example:

string env = @"
       This is an error.
       KEY1=VAL
       =VAL
       KEY2=${KEY3}
";
new EnvParser().Parse(env);

There are three errors in the data source:

• The line: This is an error. does not have a key-value pair format.
• The line =VAL has a key with empty string.
• The line KEY2=${KEY3} has an embedded variable that does not exist in the current process.

The parser should throw an exception with the three errors found instead of doing it one at a time.

[MrDave1999]

This issue is resolved by PR #18