Add functionality for finding the protractor installation and for Internet Explorer driver

Replaced hard-coded path to protractor/webdriver_manager by recursive search in higher-level directories.
Used caching of directory to prevent repeated search. 
Some data:
A `console.log` of the ‘result’ var inside the while in the `getProtractorDir()` method:
```
/Users/iuga/test/node_modules/gulp-protractor/node_modules
..//Users/iuga/test/node_modules/gulp-protractor/node_modules
../..//Users/iuga/test/node_modules/gulp-protractor/node_modules
../../..//Users/iuga/test/node_modules/gulp-protractor/node_modules

```
I think that is adding the ../ before the absolute path but should be after.

I changed:
```
result = "../“ + result;
```
for
```
result = result + "../“;
```
and the result is: 
```
/Users/iuga/test/node_modules/gulp-protractor/node_modules
/Users/iuga/test/node_modules/gulp-protractor/node_modules../
/Users/iuga/test/node_modules/gulp-protractor/node_modules../../
/Users/iuga/test/node_modules/gulp-protractor/node_modules../../../
```
It’s working now. 
What do you think? It's a valid solution?