Color ordering fix

[jmenashe]

Modified pattern coloring process to apply coloring in an order consistent with configured color lists and regex groups.

Fixes #215.

[CoelacanthusHex]

It cause an error:

Traceback (most recent call last):
  File "/usr/bin/grcat", line 238, in <module>
    add2list(clist, m, pattern['colours'])
  File "/usr/bin/grcat", line 105, in add2list
    clist.append((m.start(group+1), m.end(group+1), patterncolour[group]))
IndexError: list index out of range

when I use for journalctl
It also lead wrong color for gpg

[PBudmark]

As I stated in recent comment to issue #215, this is actually no error, but could get some clarifications in documentation.

The first color in color list refers th the whole matched string, and following colors refer to the individual groups