Move RocksDB to a Git Submodule

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "deps/rocksdb/rocksdb"]
+	path = deps/rocksdb/rocksdb
+	url = https://github.com/facebook/rocksdb.git

README.md

@@ -51,13 +51,27 @@ There are multiple ways you can find help in using LevelDB in Node.js:
 
 See the [contribution guide](https://github.com/Level/community/blob/master/CONTRIBUTING.md) for more details.
 
+### Git Submodules
+
+This project uses Git Submodules. This means that you should clone it recursively if you're planning on working on it:
+
+```bash
+$ git clone --recurse-submodules https://github.com/Level/leveldown.git
+```
+
+Alternatively, you can initalize submodules inside the cloned folder:
+
+```bash
+$ git submodule update --init --recursive
+```
+
 ### Windows
 
 A large portion of the Windows support comes from code by [Krzysztof Kowalczyk](http://blog.kowalczyk.info/) [@kjk](https://twitter.com/kjk), see his Windows LevelDB port [here](http://code.google.com/r/kkowalczyk-leveldb/). If you're using LevelUP on Windows, you should give him your thanks!
 
 ## Prebuilt Binaries
 
-`rocksdb` uses `prebuild` and `prebuild-install` for handling prebuilt binaries. See [this list](https://github.com/Level/rocksdb/releases) of supported prebuilt platform binaries. When installing rocksdb `prebuild-install` will install prebuilt binaries from GitHub if they exist and fallback to a compile step if they don't.
+`rocksdb` uses `prebuild` and `prebuild-install` for handling prebuilt binaries. See [this list](https://github.com/Level/rocksdb/releases) of supported prebuilt platform binaries. When installing rocksdb `prebuild-install` will install prebuilt binaries from GitHub if they exist and fallback to a compile step if they don't.
 
 If you are working on `rocksdb` and want to re-compile the C++ code it's enough to do `npm install`.
 
@@ -72,4 +86,4 @@ Copyright © 2012-present `rocksdb` [contributors](https://github.com/level/
 
 `rocksdb` builds on the excellent work of the LevelDB and Snappy teams from Google and additional contributors to the LevelDB fork by Facebook. LevelDB and Snappy are both issued under the [New BSD Licence](http://opensource.org/licenses/BSD-3-Clause).
 
-[level-badge]: http://leveldb.org/img/badge.svg
+[level-badge]: http://leveldb.org/img/badge.svg

binding.gyp

@@ -52,7 +52,7 @@
           }]
         ]
       , "dependencies": [
-            "<(module_root_dir)/deps/leveldb/leveldb.gyp:leveldb"
+            "<(module_root_dir)/deps/rocksdb/rocksdb.gyp:rocksdb"
         ]
       , "include_dirs"  : [
             "<!(node -e \"require('nan')\")"