v2.1.2: Updated `func (e *E) Error() string` implementation to handle…

… nil pointer references.

docs update

v2.1.0 (#18)

v2.0.1: interface implementation updates (#16)

V2.0.0 release (#15)

update CHANGELOG.md

Full rewrite (#14)

This release is a full rewrite of the `errors` package. See the README for further details.
#### Added
* `Caller` interface
* `Error` interface
* Exported methods
  - `Errorf(msg string, data ...interface{}) Error`
  - `GetCaller(err error) Caller`
  - `Has(err, test error) bool`
  - `Is(err, test error) bool`
  - `Trace(e error) Error`
  - `Track(e error) Error`

#### Changed
* Exported methods
  - `New(code std.Code, msg string, data ...interface{}) *Err`
    - `New(msg string) Error`
  - `Wrap(err error, code std.Code, msg string, data ...interface{}) *Err`
    - `Wrap(e error, msg string, data ...interface{}) Error`
#### Removed
* Exported methods
  - `From(code std.Code, err error) *Err`
* Support for error codes
* Support for sanitized vs raw error messages
* Support for HTTP status codes

fix message formatting (#13)

Fix concurrency issues (#12)

implement Trace method (#11)