Make sure element assignment is handled correctly

Add spec examples for assignment of type x[i] = y
for all cops that have special logic for assignments.
Fix problems where they are found (just one place).
Merge pull request #1489 from jonas054/fix_missed_assignment

Make sure element assignment is handled correctly
[Fix #1484] EmptyLinesAroundAccessModifier incorrectly finds a violation inside method calls with names identical to an access modifier.
Merge pull request #1491 from dblock/bug-1484

Fix `EmptyLinesAroundAccessModifier` incorrectly finding a violation inside method calls with names identical to an access modifier.
[Fix #1430] Add option --except for disabling cops on command line

Add a companion to the --only option. This option will
disable the given cops (comma separated list).
Merge pull request #1497 from jonas054/1430_except_option

[Fix #1430] Add option --except for disabling cops on command line
Abort when auto-correct causes an infinite loop.
Added periods where periods are due.
Merge pull request #1492 from dblock/conflicting-cops

Abort when auto-correct causes an infinite loop.
Merge pull request #1499 from dblock/readme-dots

Added periods where periods are due.
Require digest/md5 for ProcessedSource#checksum
Merge pull request #1502 from jonas054/require_digest_md5

Require digest/md5 for ProcessedSource#checksum
Fix bug in how Exclude works

Two problems fixed:
1) We make Exclude paths absolute at one point to simplify
handling later on. This needs to be done for all Exclude
properties, not only AllCops/Exclude.
2) When checking if a file matches a pattern we must try
both the absolute and the relative path, since patterns
of both varieties exist.
Merge pull request #1498 from jonas054/fix_exclude_bug

Fix bug in how Exclude works
[Fix #1500] Remove double handling of elsif in IndentationWidth

The fact that elsif bodies were checked twice could cause
auto-correction to become unstable and indent indefinitely.
The reason was that one check was relative to the if keyword,
the other to the elsif keyword. So if these were not aligned,
and the ElseAlignment cop was not enabled, there would always
be an offense to correct.
Merge pull request #1505 from jonas054/1500_fix_indentation_width

[Fix #1500] Remove double handling of elsif in IndentationWidth
Remove :focus left in spec by mistake
[Fix #1501] Make sure offenses are printed after infinite loop

Makes it easier to figure out what went wrong.
Merge pull request #1513 from jonas054/1501_infinite_loop_reporting

[Fix #1501] Make sure offenses are printed after infinite loop
Remove arrays wrapping a single string in inspect_source calls

New contributors to the project make the mistake of always
using arrays for the code given to inspect_source. It's not
so strange given that there are so many places in the code
today doing the same thing.