Add ability to strip arbitrary prefix

[mikeymc]

In response to #5

This feature adds the ability to strip an arbitrary prefix from the input file name.

In our last two projects, we found it difficult to figure out how to strip a prefix from a file name to be placed into the key of the $templateCache.put(). We wished there was a way to simply strip some arbitrary prefix, but that feature did not exist. We saw the -b/--basedir option, but we could not figure out how to use it properly. As a result, we found ourselves having to change directories to the level where the relative path to the file would wind up being what we wanted to see in the key of the $templateCache.put(). This was a drag. It seems others have also had similar issues with the --basedir option. So, we added the ability to strip an arbitrary prefix.

The behavior of the feature is specified in the tests that accompany this pull request.

In short, to strip an arbitrary prefix, run the following:

./path/to/ng-html2js path/to/file.tmpl -s path/to/

this will yield:

$templateCache.put('file.tmpl', 'the-rest-of-the-magic-goodness')

[mikeymc]

Tests will fail until CI switches to jasmine

[yaru22]

There seems to be conflicts after merging pr #7. Could you merge with the latest for this PR?