Move home variable into readline ifdef
If readline is enabled add readline to libraries to link
display multiple authors better.

Before:
Copyright (c) 2013 ["a", "b"]

After:
Copyright (c) 2013 a, b
"spec.author" is better for single-author gems.

"spec.author=" expects a String represents a single author.
"spec.authors=" expects an Array which is a list of multiple authors.

http://guides.rubygems.org/specification-reference/
Check home is null
gc: add comments for Generational Mode
String `=~` and `match` to work with pluggable Regexp; close #1398
Merge branch 'master' of github.com:mruby/mruby
Merge pull request #1400 from carsonmcdonald/readlinewarnfix

Move home variable into readline ifdef
Merge pull request #1399 from carsonmcdonald/readlinelinkfix

If readline is enabled add readline to libraries to link
resolve conflict
Merge pull request #1402 from mattn/check_home_is_null

Check home is null
Merge pull request #1403 from Fleurer/comments-generational-gc

add comments for Generational Mode in gc.c
introduce incremental_gc_step()
rename mrb_garbage_collect() to mrb_full_gc()
gc: replace comment "a round of GC" to "a GC cycle"
Fix mrbc error for space included path
introduce gc_mark_gray_list(), and cleanup redaunt code with it
rename variable_gray_list to atomic_gray_list
fix warning