Refactored and deprecation of Generate()

Introduced:

Validate() error                    // Validate if the CEF message is according to the specification.
String() (string, error)            // String constructs and returns a CEF message string.
Build() (CefEvent, error)           // Build constructs and returns a CEF message according to CefEvent.
Read(line string) (CefEvent, error) // Read parses a CEF message string and populates the CefEvent struct with the extracted data.
Log() error                         // Log attempts to generate a CEF message from the current CefEvent and logs it to the standard output.
escapeEventData() error             // escapeEventData will try to escape all data properly in the struct according the Common Event Format.

What's Changed

• Fix/add docstrings by @pcktdmp in #30
• Feat/refactor by @pcktdmp in #31

Full Changelog: v0.3.0...v0.4.0