Improvements of disable/enablehyphenation

Now it continues to work even if you load a different language. Ex:

\selectlanguage{langx}

some hyphenated text with langx settings

\disablehyphenation

some non-hyphenated text with langx settings

\selectlanguage{langy}

some non-hyphenated text with langy settings

\enablehyphenation

some hyphenated text with langy settings
Documenting hyphenation enabling/disabling
Merge pull request #47 from eroux/master

Documentation and improvements of enable/disablehyphenation