[TASK] Condition require-file statement for no longer existing file
Merge pull request #206 from NamelessCoder/62compat

[TASK] Condition require-file statement for no longer existing file
[TASK] Update Travis script to install extension

Needed since Flux is no longer installed in the source used.
[BUGFIX] Use of an incorrect field name in two parameters
[BUGFIX] Prevent inclusion of class file if file does not exist
[TASK] Install VHS as dependency in Travis script

Needed for Grid operation tests.