Allow dots and slashes in tags

[mhils]

Hi! First off, thanks for the fantastic work here @nomeata. 😊

I stumbled upon arbtt earlier today and started working on an initial configuration. One thing I tried was creating tags for particular websites. Capturing this works great with a Chrome addon, but the output of arbtt-stats isn't as beautiful as it maybe could be:

$ arbtt-stats -c "web"
Statistics for category "web"
=============================
_________________Tag______|______Time_|_Percentage_
web:arbtt_nomeata_de_doc_ |     7m00s |      10.14
         (unmatched time) |  1h02m00s |      89.86

I feel that it would be much nicer to have this:

$ arbtt-stats -c "web"
Statistics for category "web"
=============================
_________________Tag______|______Time_|_Percentage_
web:arbtt.nomeata.de/doc/ |     7m00s |      10.14
         (unmatched time) |  1h02m00s |      89.86

The same issue occurs for folders, where / and \ are replaced with underscores as well (Program_Files__x86__Google_Chrome_Application_chrome_exe).

This PR makes replaceForbidden a bit more lax by allowing ., /, and \. As \ is a bit problematic as an escape character, I decided to replace it with a forward slash. While maybe not ideal, it makes Windows paths much nicer. Maybe it's also nice to allow parantheses, but I wanted to keep it minimal for now and only include the characters I would care about.

Thanks!
Max

[nomeata]

I wonder why I disallowed strange characters in the first place. Maybe I should just allow them all!

For consistency, that would probably call for the syntax

tag "foo:bar"

i.e. quotes when an explicitly written tag has special characters.

[mhils]

FWIW, arbtt-dump crashes on "Skype™ - username" on Windows, so maybe that is why:

PS > arbtt-dump.exe
2018-02-20 20:53:36 (688ms inactive):
    ( ) \Device\HarddiskVolume4\Windows\explorer.exe: Program Manager
    ( ) \Device\HarddiskVolume4\Program Files (x86)\Google\Drive\googledrivesync.exe: Backup & Sync
    ( ) \Device\HarddiskVolume4\Program Files\WindowsApps\Microsoft.WindowsStore_11801.1001.6.0_x64__8wekyb3d8bbwe\WinStore.App.exe: Microsoft Store
    ( ) \Device\HarddiskVolume4\Windows\System32\ApplicationFrameHost.exe: Microsoft Store
    ( ) \Device\HarddiskVolume4\Program Files (x86)\Skype\Phone\Skype.exe: Skypearbtt-dump.exe: <stdout>: commitBuffer: invalid argument (invalid character)

But yes - happy to do any changes that can be done with my nonexistent Haskell knowledge. :-)