Remove need for character escaping

First, thanks for this awesome plugin which has made my life at least 10% more joyful!

One thing I disliked though was the need to escape special characters with 2 backslashes, so here's my attempt to fix this. It does this by using extended POSIX regex syntax (`grep -E`) and getting rid of the call to `eval`. The default searches are adjusted and still seem to work fine, I also tried running the included tests but ran into problems with Vagrant:

```
$ ./run-tests 
Bringing machine 'ubuntu' up with 'virtualbox' provider...
==> ubuntu: Box 'hashicorp/precise32' could not be found. Attempting to find and install...
    ubuntu: Box Provider: virtualbox
    ubuntu: Box Version: >= 0
The box 'hashicorp/precise32' could not be found or
could not be accessed in the remote catalog. If this is a private
box on Vagrant Cloud, please verify you're logged in via
`vagrant login`. Also, please double-check the name. The expanded
URL and error message are shown below:

URL: ["https://vagrantcloud.com/hashicorp/precise32"]
Error: Maximum (10) redirects followed
Running test suite on ubuntu from: /vagrant/test/run-tests-within-vm

VM must be created before running this command. Run `vagrant up` first.
==> ubuntu: VM not created. Moving on...
Bringing machine 'centos' up with 'virtualbox' provider...
==> centos: Box 'chef/centos-6.5' could not be found. Attempting to find and install...
    centos: Box Provider: virtualbox
    centos: Box Version: >= 0
The box 'chef/centos-6.5' could not be found or
could not be accessed in the remote catalog. If this is a private
box on Vagrant Cloud, please verify you're logged in via
`vagrant login`. Also, please double-check the name. The expanded
URL and error message are shown below:

URL: ["https://vagrantcloud.com/chef/centos-6.5"]
Error: Maximum (10) redirects followed
Running test suite on centos from: /vagrant/test/run-tests-within-vm

VM must be created before running this command. Run `vagrant up` first.
==> centos: VM not created. Moving on...

Tests failed!
```

I don't have any experience with Vagrant, but in case there's an easy fix please let me know and I'll give it another try.