Add meta EIP for Spurious Dragon (ethereum#607)

* Add meta EIP for Spurious Dragon

* assign no. 607 to Spurious Dragon meta-eip

* add links to spurious dragon meta

* links in Spurious Dragon meta-EIP

* add references and aliases to eip-607

EIPS/eip-607.md

@@ -0,0 +1,35 @@
+
+## Preamble
+
+    EIP: 607
+    Title: Hardfork Meta: Spurious Dragon
+    Author: Alex Beregszaszi
+    Type: Meta
+    Status: Final
+    Created: 2017-04-23
+    Requires: 155, 160, 161, 170
+
+## Abstract
+
+This specifies the changes included in the hard fork named Spurious Dragon.
+
+## Specification
+
+- Codename: Spurious Dragon
+- Aliases: State-clearing
+- Activation:
+  - Block >= 2,675,000 on Mainnet
+  - Block >= 1,885,000 on Morden
+- Included EIPs:
+  - [EIP 155](eip-155.md) (Simple replay attack protection)
+  - [EIP 160](eip-160.md) (EXP cost increase)
+  - [EIP 161](eip-161.md) (State trie clearing)
+  - [EIP 170](eip-170.md) (Contract code size limit)
+
+## References
+
+1. https://blog.ethereum.org/2016/11/18/hard-fork-no-4-spurious-dragon/
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).