Migrate to govendor to avoid limitations of godep

- over the course of a project history every maintainer needs to update
  its dependency packages, the problem essentially with godep is manipulating
  GOPATH - this manipulation leads to static objects created at different locations
  which end up conflicting with the overall functionality of golang.

  This also leads to broken builds on many platforms. There is no easier way out of
  this other than asking users to do 'godep restore' all the time which perhaps as
  a practice doesn't sound clean, also has its own set of problems.

- govendor on the other hand is a right tool but a stop gap tool until we wait for
  golangs official 1.5 version which fixes this vendoring issue once and for all.

- govendor makes sure that the import paths are re-written instead of manipulating
  GOPATH.

  This has advantages
    - no more compiled objects being referenced in GOPATH and build time GOPATH
      manging which leads to conflicts.
    - proper import paths referencing the exact package a project is dependent on.

  govendor is simple and provides the minimal necessary tooling to achieve this.

  For now this is the right solution.

typed-errors.go

@@ -38,12 +38,6 @@ func (e errInvalidACL) Error() string {
 	return "Invalid ACL Type ‘" + e.acl + "’. Valid types are [private, public, readonly]."
 }
 
-type errNotConfigured struct{}
-
-func (e errNotConfigured) Error() string {
-	return "‘mc’ not configured."
-}
-
 type errNotAnObject struct {
 	url string
 }
@@ -58,15 +52,6 @@ func (e errInvalidArgument) Error() string {
 	return "Incorrect usage, please use \"mc config help\""
 }
 
-type errUnsupportedScheme struct {
-	scheme string
-	url    string
-}
-
-func (e errUnsupportedScheme) Error() string {
-	return "Unsuppported URL scheme: " + e.scheme + " URL: ‘" + e.url + "’"
-}
-
 type errInvalidGlobURL struct {
 	glob    string
 	request string
@@ -151,12 +136,6 @@ func (e errTargetIsNotDir) Error() string {
 	return "Target ‘" + e.URL + "’ is not a folder."
 }
 
-type errTargetNotFound errInvalidURL
-
-func (e errTargetNotFound) Error() string {
-	return "Target folder ‘" + e.URL + "’ does not exist."
-}
-
 type errSourceNotRecursive errInvalidURL
 
 func (e errSourceNotRecursive) Error() string {