Update readme to reflect v1 changes

Signed-off-by: Knut Ahlers <knut@ahlers.me>

README.md

@@ -1,4 +1,3 @@
-[![Go Report Card](https://goreportcard.com/badge/github.com/Luzifer/korvike)](https://goreportcard.com/report/github.com/Luzifer/korvike)
 ![](https://badges.fyi/github/license/Luzifer/korvike)
 ![](https://badges.fyi/github/downloads/Luzifer/korvike)
 ![](https://badges.fyi/github/latest-release/Luzifer/korvike)
@@ -9,31 +8,14 @@
 
 ## Available functions
 
+Starting with `v1.0.0` Korvike is based on the [sprig functions collection](https://masterminds.github.io/sprig/) with some additions:
+
 - `{{ .<variable name> }}`  
   Take key-value pairs from the CLI and replace them inside the template
   ```console
   $ echo "{{ .foo }}" | korvike -v foo=bar
   bar
   ```
-- `{{ b64decode <string> }}`  
-  Decodes the string with base64 [StdEncoding](https://golang.org/pkg/encoding/base64/#pkg-variables)
-  ```console
-  $ echo '{{ b64decode "SGVsbG8gV29ybGQ=" }}' | korvike
-  Hello World
-  ```
-- `{{ b64encode <string> }}`  
-  Encodes the string with base64 [StdEncoding](https://golang.org/pkg/encoding/base64/#pkg-variables)
-  ```console
-  $ echo '{{ b64encode "Hello World" }}' | korvike
-  SGVsbG8gV29ybGQ=
-  ```
-- `{{ env <variable name> [default value] }}`  
-  Read environment variables and replace them inside the template
-  ```console
-  $ export FOO=bar
-  $ echo '{{ env "FOO" }}' | korvike
-  bar
-  ```
 - `{{ file <file name> [default value] }}`  
   Read a file and place it inside the template
   ```console
@@ -41,36 +23,12 @@
   $ echo '{{ file "hello" }}' | korvike
   Hello World
   ```
-- `{{ hash <algo> <string> }}`  
-  Hash string with given algorithm (supported algorithms: md5, sha1, sha256, sha512)
-  ```console
-  $ echo '{{ hash "sha256" "this is a test" }}' | korvike
-  2e99758548972a8e8822ad47fa1017ff72f06f3ff6a016851f45c398732bc50c
-  ```
-- `{{ join <string> <delim> }}`  
-  Joins the given slice of strings with given delimiter.
-  ```console
-  $ echo '{{ join (split "a,b,c" ",") "|" }}' | korvike
-  a|b|c
-  ```
 - `{{ markdown <source> }}`  
   Format the source using a markdown parser
   ```console
   $ echo '{{ markdown "# headline" }}' | korvike
   <h1>headline</h1>
   ```
-- `{{ now <format string> }}`  
-  Format the current date into the template (uses [Go time format](https://golang.org/pkg/time/#Time.Format))
-  ```console
-  $ echo '{{ now "2006-01-02 15:04:05" }}' | korvike
-  2017-04-17 16:27:34
-  ```
-- `{{ split <string> <sep> }}`  
-  Splits the given string by given separator.
-  ```console
-  $ echo '{{ range (split "a,b,c" ",") }}{{ . }} {{ end }}' | korvike
-  a b c
-  ```
 - `{{ tplexec (file "my.tpl") }}`  
   Execute the given template with the same function set and variables as the parent template.
   ```console