CocoaPods/CocoaPods — pull request #408 by siuying (2012-07-17 01:56:36+00:00)
Title: Add Pod::Podfile::Informative error which show lines in Podfile (Re: #403)

Improve informative error message in podfile.

For following Podfile:

```
platform :iOS

pod 'CoconutKit'
```

run ```pod install``` show following error:

```
[!] Unsupported platform: platform must be one of [:ios, :osx]
(/Users/siuying/Documents/workspace/Sample/Podfile:1:in `block in from_file')
```