Rename --pull_gems to --pull-gems

doc/mrbgems/README.md

@@ -26,7 +26,7 @@ A remote GIT repository location for a GEM is also supported:
 	conf.gem :bitbucket => 'mruby/mrbgems-example', :branch => 'master'
 
 To pull all gems from remote GIT repository on build, call ```./minirake -p```, 
-or ```./minirake --pull_gems```.
+or ```./minirake --pull-gems```.
 
 NOTE: `:bitbucket` option supports only git. Hg is unsupported in this version.
 

minirake

@@ -317,7 +317,7 @@ class RakeApp
       "Require MODULE before executing rakefile."],
     ['--tasks',    '-T', GetoptLong::NO_ARGUMENT,
       "Display the tasks and dependencies, then exit."],
-    ['--pull_gems','-p', GetoptLong::NO_ARGUMENT,
+    ['--pull-gems','-p', GetoptLong::NO_ARGUMENT,
       "Pull all git mrbgems."],
     ['--trace',    '-t', GetoptLong::NO_ARGUMENT,
       "Turn on invoke/execute tracing."],
@@ -403,7 +403,7 @@ class RakeApp
       require value
     when '--tasks'
       $show_tasks = true
-    when '--pull_gems'
+    when '--pull-gems'
       $pull_gems = true
     when '--trace'
       $trace = true