Add Testcases, Fix anusvara<->മ complications

[subins2000]

• Allows typing "മ്ലേച്ചം" (mlEchcham) (Fixes bug of anusvara coming at beginning)

  
  anusvara [["m"]] => ["ം","ം","മ"]
  anusvara "m_" =>  ["ം","ം","മ"]
  anusvara({:accept_if => :ends_with}, "m" => ["ം","ം","മ"])
  anusvara({:accept_if => :in_between}, "m" => ["ം","ം","മ"])

consonants ["ma"] => "മ"

It used to give `mlEchcham =>  ംലേച്ചം`. There also was custom mapping for `mv => മ്വ`. These custom mappings for മ is not needed anymore with this change.

* Add unit tests for Malayalam