Add Lexer test for separating tokens without whitespace.

Tokens do not need to be separated by whitespace, e.g. a[b] is 4 tokens.
Add a test for that (ignored for now because the lexer is not yet implemented.)
Remove *.mj/*.java file name requirement

It is not mentioned in the spec and could lead to problems with
automated tests by the course instructors (their test files might be
named differently).
CLI: Make --lextest not take a string, add help string

opt[String] would imply a parameter of the form "--lextest <value>", but
the specification on the assignment sheet says --lextest does not take
any values but the file name (which is a separate parameter).
Merge pull request #24 from jspam/011-lextest-parameter

CLI: Make --lextest not take a string, add help string
Merge pull request #23 from jspam/010-file-extensions

Remove *.mj/*.java file name requirement
Convert case classes to case objects
Merge pull request #21 from soc/topic/case-objects

Convert case classes to case objects
Merge pull request #17 from jspam/008-moar-lexer-tests

Add Lexer test for separating tokens without whitespace.