Add new commands

Run `gcdmc` or `gcmmc` in order to merge the latest remote [develop|master] state into the current branch. In more detail: 
- checkout [develop|master] branch
- pull [develop|master] branch
- checkout latest branch
- merge [develop|master] branch to latest branch

plugins/git/git.plugin.zsh

@@ -82,6 +82,8 @@ alias gcp='git cherry-pick'
 alias gcpa='git cherry-pick --abort'
 alias gcpc='git cherry-pick --continue'
 alias gcs='git commit -S'
+alias gcdmc='git checkout develop && git pull && git checkout - && git merge develop'
+alias gcmmc='git checkout master && git pull && git checkout - && git merge master'
 
 alias gd='git diff'
 alias gdca='git diff --cached'