Similar to git, we now ignore options which have no value.
Previously it would not handle it consistently, and throw a parsing
error the first time the cache was built.

Afterwards, it was fully usable though.
Now we specifically check for the case of no-value options instead.

Closes #349

This allows us to use the main thread to parse stderr to get progress,
and resolve assertion failures hopefully once and for all.

Relates to #301

Test was adjusted as well to parse only a single file which simulates
stderr output.

* Previously we could fail to parse the last line within a read buffer,
  which is now fixed.
* Added a test to verify our *slow* line parsing works as expected.

* config parser now handles quoted values correctly. This doesn't hamper
  multi-line support.
* added regression test to travis to assure we will be warned if we
  rewrite and break the user's .gitconfig file
* only rewrite configuration files if we actually called a mutating
  method on the writer. Previously it would always rewrite it.

Fixes #285

Even though the test-csae only verifies this spec:
	+refs/pull/*:refs/heads/pull/*
I could locally verify that it indeed handles other ones just as well:
	+refs/pull/*:refs/pull/*

Fixes #243

GIT_PYTHON_TRACE would actually fail (now) if we debugged archive operations.

Related to #239

We implement it as described in this article:
http://stackoverflow.com/questions/1557183/is-it-possible-to-include-a-file-in-your-gitconfig

Thus we handle

* cycles
* relative and absolute include paths
* write-backs in case of writable GitConfigParser instances

Fixes #201

This brings us much closer to what git can do, and should at least prevent errors while reading
configuration files (which would break a lot of features, like handling of remotes since these rely
reading configuration files).

Fixes #112

It works as expected by me at least.
Related to #71