Fix go get path in README.md and panic help

Using:
  go get github.com/maruel/panicparse/cmd/pp

will retrieve 1.5.0. But now that 2.0.0 is in the sumdb, I can't remove
it anymore, hence a new 2.0.1 release that fix the path in the README
and panic's help.

Author: maruel

README.md

@@ -16,7 +16,7 @@ panicparse helps make sense of Go crash dumps:
 
 ## Features
 
-See [v2.0.0 blog post](https://maruel.ca/post/panicparse-2.0.0/).
+See [v2.0.1 blog post](https://maruel.ca/post/panicparse-2.0.1/).
 
    * **New in v2.0.0!**: Full go module support.
    * **New in v2.0.0!**: Race detector support.
@@ -50,7 +50,7 @@ Ruel](https://github.com/maruel) and
 
 ## Installation
 
-    go get github.com/maruel/panicparse/cmd/pp
+    go get github.com/maruel/panicparse/v2/cmd/pp
 
 
 ## Usage
@@ -162,7 +162,7 @@ you may be running the _Perl PAR Packager_ instead of panicparse.
 You have two choices, either you put `$GOPATH/bin` at the beginning of `$PATH`
 or use long name `panicparse` with:
 
-    go get github.com/maruel/panicparse
+    go get github.com/maruel/panicparse/v2
 
 then using `panicparse` instead of `pp`:
 

cmd/panic/main.go

@@ -7,16 +7,16 @@
 // It is a tool to help test pp, it is used in its unit tests.
 //
 // To install, run:
-//   go install github.com/maruel/panicparse/cmd/panic
+//   go install github.com/maruel/panicparse/v2/cmd/panic
 //   panic -help
 //   panic str |& pp
 //
 // Some panics require the race detector with -race:
-//   go install -race github.com/maruel/panicparse/cmd/panic
+//   go install -race github.com/maruel/panicparse/v2/cmd/panic
 //   panic race |& pp
 //
 // To use with inlining disabled, build with -gcflags '-l' like:
-//   go install -gcflags '-l' github.com/maruel/panicparse/cmd/panic
+//   go install -gcflags '-l' github.com/maruel/panicparse/v2/cmd/panic
 package main
 
 // To add a new panic stack signature, add it to types type below, keeping the
@@ -112,7 +112,7 @@ func recurse(i int) {
 func panicRaceDisabled(name string) {
 	help := "'panic %s' can only be used when built with the race detector.\n" +
 		"To build, use:\n" +
-		"  go install -race github.com/maruel/panicparse/cmd/panic\n"
+		"  go install -race github.com/maruel/panicparse/v2/cmd/panic\n"
 	fmt.Fprintf(stdErr, help, name)
 }
 
@@ -314,7 +314,7 @@ var types = map[string]struct {
 			// https://github.com/golang/go/issues/20588
 			//
 			// Repro:
-			//   go install -race github.com/maruel/panicparse/cmd/panic; panic asleep
+			//   go install -race github.com/maruel/panicparse/v2/cmd/panic; panic asleep
 			var mu sync.Mutex
 			mu.Lock()
 			mu.Lock()