Add meta EIP for Tangerine Whistle (EIP 150 Hard Fork) (#608)

* Add meta EIP for EIP 150 Hard Fork

* Rename to Tangerine Whistle

* link to EIP-150 in meta-hf spec

* assign no. 608 to Tangerine Whistle meta-eip

* add references and aliases to EIP150 meta-EIP

EIPS/eip-608.md

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+## Preamble
+
+    EIP: 608
+    Title: Hardfork Meta: Tangerine Whistle
+    Author: Alex Beregszaszi
+    Type: Meta
+    Status: Final
+    Created: 2017-04-23
+    Requires: 150
+
+## Abstract
+
+This specifies the changes included in the hard fork named Tangerine Whistle (EIP 150).
+
+## Specification
+
+- Codename: Tangerine Whistle
+- Aliases: EIP 150, Anti-DoS
+- Activation:
+  - Block >= 2,463,000 on Mainnet
+- Included EIPs:
+  - [EIP 150](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-150.md) (Gas cost changes for IO-heavy operations)
+  
+## References
+
+1. https://blog.ethereum.org/2016/10/13/announcement-imminent-hard-fork-eip150-gas-cost-changes/
+2. https://blog.ethereum.org/2016/10/18/faq-upcoming-ethereum-hard-fork/
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).