[#201] Added support for CocoaPods-version.yml

Add Specification#prefix_header_contents which does not take a pch file, but a string of code to be appended to the Pods pch file.

Spec create

see [this
discussion](https://github.com/CocoaPods/CocoaPods/commit/6bedfe0baac10e4e6ff30968b18acd111c143e1e#commitcomment-1212777)
for details

added check for `project_podfile` variable and only if it's not nil wi
will check `exist?`

in error_report

- added semanting versioning notice
- warning if a spec description or summary does not ends with a dot
- requires octokit gem
- added awesome-print development gem
- removed appledoc options from spec template
- removed range attribute for license from the spec template

Pod::Podfile::TargetDefinition.

* If no workspace is specified, then the basename of the default
  target's project will be used.
* If no workspace is specified and multiple projects have been
  specified (in several target definitions), an Informative error
  will be raised indicating that the user should specify one
  explicitely.

NOTE: The workspace code doesn’t actually exist yet, it’s the last thing to do in this branch.