Remove Gemfile.lock

Gemfile.lock lists many gems that are not dependencies of FakeFS, and has too
strict version requirements for actual dependencies.
It is already in the .gitignore file, I'm not sure why it is committed at all.

Move dependency version requirements to Gemfile
Remove fakefs.gemspec because it is generated

fakefs.gemspec is generated by Jeweler based on the Rakefile.

It was committed at c37ec381, then later added to the .gitignore file at
f42b1e90
add license information to gemspec generator

Canonical source of gemspec is in the Rakefile.
Replay of 951d4d477cf19118a404d668fe72e05a1e42b4d5
bump version to 0.4.3

To release all the changes that have occured since the 0.4.2 version bump on
November 24, 2012