Add alias and README to git-flow plugin (#5129)

plugins/git-flow/README.md

+# Git flow plugin installation
+
+```bash
+git clone https://github.com/robbyrussell/oh-my-zsh.git 
+
+cp oh-my-zsh/plugins/git-flow/git-flow.plugin.zsh ~/.git-flow-completion.zsh
+
+vim ~/.zshrc
+
+# Which plugins would you like to load? (plugins can be found in ~/.oh-my-zsh/plugins/*)
+# Custom plugins may be added to ~/.oh-my-zsh/custom/plugins/
+# Example format: plugins=(rails git textmate ruby lighthouse)
+# Add wisely, as too many plugins slow down shell startup.
+
+plugins=(git git-flow)
+      
+source ~/.git-flow-completion.zsh
+```
+## Your new git-flow alias 
+
+```bash
+alias gfl='git flow'
+alias gfli='git flow init'
+alias gcd='git checkout develop'
+alias gch='git checkout hotfix'
+alias gcr='git checkout release'
+alias gflf='git flow feature'
+alias gflh='git flow hotfix'
+alias gflr='git flow release'
+alias gflfs='git flow feature start'
+alias gflhs='git flow hotfix start'
+alias gflrs='git flow release start'
+alias gflff='git flow feature finish'
+alias gflhf='git flow hotfix finish'
+alias gflrf='git flow release finish'
+``` 

plugins/git-flow/git-flow.plugin.zsh

@@ -22,9 +22,19 @@
 
 #Alias
 alias gfl='git flow'
+alias gfli='git flow init'
 alias gcd='git checkout develop'
 alias gch='git checkout hotfix'
 alias gcr='git checkout release'
+alias gflf='git flow feature'
+alias gflh='git flow hotfix'
+alias gflr='git flow release'
+alias gflfs='git flow feature start'
+alias gflhs='git flow hotfix start'
+alias gflrs='git flow release start'
+alias gflff='git flow feature finish'
+alias gflhf='git flow hotfix finish'
+alias gflrf='git flow release finish'
 
 _git-flow ()
 {