Add supported Platforms (#119)

PLATFORMS.md

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+# Supported Platforms
+
+Following platforms are supported by Cypress:
+
+### macOS
+
+Supports Mac OS 10.9 (Mavericks) or later, only 64bit binaries are provided for macOS
+
+### Linux
+
+The prebuilt `ia32` and {`i686`} and `x64` (`amd64`) binaries of Cypress are built on Ubuntu 12.04, the `arm` binary is built against ARM v7 with hard-float ABI and NEON for Debian Wheezy.
+
+Whether the prebuilt binary can run on a  distribution dependson whether the distribution includes the libraries that Cypress is linked to on the building platform, so only Ubuntu 12.04 is guaranteed to work, but following platforms are also verified to be able to run the prebuilt binaries of Cypress:
+
+* Ubuntu 12.04 and later
+* Fedora 21
+* Debian 8
+
+### Windows
+
+The windows are on development, coming soon!